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Scanning optical frequency domain reflectometer

1. Called by Scanning OFDR 2 2 vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 1 LVClass Name Description Cluster error in Input error cluster Outputs 3 LVClass Name Description String data Cluster error out Output error cluster Boolean Sweeping Indicates whether or not the Agilent 81680A tunable laser is currently sweeping VI description This VI queries the state of the Agilent 81680A tunable laser to determine if it is currently sweeping 38 Agilent Start Wavelength vi Called by Agilent Startup Sequence vi Custom VIs called None Labview VIs called None Inputs 3 LVClass Name Description Cluster error in Input error cluster Digital GPIB Address GPIB address of the Agilent 81680A tunable laser Digital Start Wavelength Requested sweep start wavelength nm Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description This VI sets the sweep start wavelength on the Agilent 81680A tunable laser 39 Agilent Startup Sequence vi Called by Custom VIs called Scanning OFDR 2 2 vi OFDR Global vi Agilent Sweep Speed vi Agilent Sweep Mode vi Agilent Stop Wavelength vi Agilent Start Wavelength vi Agilent Power vi Agilent Laser On Off vi Agilent Cycle Number vi Labview VIs called None Inputs 6 LVClass Name Digital End WL nm Cluster error in Digital Number of Sweep Cycle Digital Power mW Digital Start WL nm ComboBox Sweep Speed
2. New peak array with changes Peak array prior to changes Description Output error cluster Updated peak array VI description This VI handles changes made to the Peak Selection and Mea surements array in the main Scanning OFDR program 64 Called by Custom VIs called Labview VIs called OpenG VIs called Load Configuration vi Load OFDR Config vi None TRef Get All FP References vi NI_LVConfig Ivlib Config Data RefNum ctl Read Key Variant __ogtk vi Inputs 4 LVClass Name Description Cluster error in no Input error cluster error TypedRefNum INI refnum Configuration file reference String Tag Description tag Only tagged controls are loaded VIRefNum VI reference Reference to the VI being configured Outputs 3 LV Class Name Description Cluster error out Output error cluster TypedRefNum INI refnum out Configuration file reference VIRefNum VI reference out Reference to the VI being configured VI description This VI calls the OpenG function Read Key Variant vi to read front panel control values of the VI specied by VI Path from a configuration file specified by INI Path only if the beginning of the control description matches Tag Read Key Variant vi is recursive so that nested controls are handled Only tags for top level controls are checked however so for controls inside clusters or arrays all controls in the array are either written or not depending on the description tag of the pare
3. output while Output 2 is the high power output Always use Output 2 for the OFDR e The optical outputs on the laser take FC APC connectors These connectors have an angle polished ferrule and generally have a green boot Do not plug FC PC flat polished connectors into the laser lsee Eric D Moore Advances in Swept Wavelength Interferometry for Precision Measurements Ph D Dissertation University of Colorado at Boulder 2011 and the references therein In particular Ch 2 provides an introduction to OFDR Ch 4 covers precision ranging measurements using OFDR and Ch 6 discusses calibrated reflectivity measurements using scanning OFDR HP Seruga Seiki D120 Motion Tower PC Controller Agilent 81680A DAQ Tunable Laser LAAAJ O i 90 H HP Polarization a Controller Interferometer O Frequency Optical fiber XX Clock Harware commands PC2 Clock signals Digital trigger signal Data signals PCI MXI interface gt E ie lt gt 3dB Coupler except as noted Switch DN 000 Manual polarization controller P OFDR 2 HE AR coated FC PC connector Interferometer A Photodetector Probe 1 Stage Stack 1 O Fiber delay line ANO i Stage Probe 2 Stack 2 Probe 3 Figure 1 A schematic diagram of the Scanning OFDR system hardware e There is a green LED labeled Active near each optical output When this light is off
4. Once data has been acquired it will be automatically displayed in the main graph area of user interface The type of data displayed in graph depends on the value of Plot Selection located directly above the graph After data has been acquired change Plot Selection to view the data processed in different ways The options for Plot Selection are Raw Data This option displays the raw unprocessed data that is currently in memory There will be one curve for each analog input channel 4 for the acquisitions made using the PCI 6115 DAQ board and 8 for acquisitions with the PXIe 4492 The vertical axis is in units of volts while the horizontal axis depends on the Clock Source used for the acquisition Internal clock acquisitions are displayed as a function of time while external clock acquisitions are displayed as a function of wavelength Fourier Transform Raw This option displays the discrete Fourier transform of the raw data currently in memory There will be one curve for each analog input channel Internal clock acquisitions are displayed as a function of frequency while external clock acquisitions are displayed as a function of time or delay Strictly speaking only the reference arm contribution to the S and P signals should be balanced For weak reflectors 4 or less it is acceptable to balance the signals in the presence of a test arm contribution For strong reflectors however this is not the case Therefore if there is a str
5. User Outputs 5 Name Canceled error out New User User out vi reference Scanning OFDR 2 2 vi Description Discard changes and close the dialog window Input error cluster Accept changes and close the dialog window The name of the user Previous users are stored in a drop down list Description Indicate whether the user canceled the operation Output error cluster Indicates whether registered user was present in the drop down list The name of the user Reference to this VI so changes to the drop down list can be saved after execution VI description This VI presents a dialog interface to register the name of the user 80 Called by Custom VIs called Labview VIs called LVClass Array Array Digital Ring LVClass Digital Digital Digital Array Resample vi Inputs 4 Name Data Frequency v time Interp Factor method Outputs 4 Name Data buffer size Effective trigger delay New start WL Resampled Data Scanning OFDR 2 2 vi OFDR Global vi Fourier Interpolation vi NI_Gmath lvlib Interpolate 1D vi Description The time sampled wavelength sweep data to be resampled onto a grid of equal optical frequency increments Frequency evolution data during the wavelength sweep Factor by which to increase the sampling density of the input Data array via Fourier interpolation prior to resam pling The interpolation method See the
6. nm s Outputs 1 LV Class Name Cluster error out Description Requested sweep end wavelength Input error cluster Requested number of sweeps Requested laser power setting Requested sweep start wavelength Requested laser tuning rate Allowable values are 0 5NM S 5NM S and 40NM S Description Output error cluster VI description This VI prepares the Agilent 81680A tunable laser for an OFDR measurement by setting the sweep start and end wavelengths laser power sweep speed and number of sweep cycles as well as turning on the optical output 40 Agilent Stop Wavelength vi Called by Agilent Startup Sequence vi Custom VIs called None Labview VIs called None Inputs 3 LVClass Name Description Cluster error in Input error cluster Digital GPIB Address GPIB address of the Agilent 81680A tunable laser Digital Stop Wavelength Requested sweep end wavelength Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description This VI sets the sweep end wavelength on the Agilent 81680A tunable laser Al Agilent Sweep Actions vi Called by Scanning OFDR 2 2 vi Sweep Agilent Laser 2 vi Custom VIs called None Labview VIs called None Inputs 3 LVClass Name Description ComboBox Action Requested action Allowable values are STOP START PAUSE and CONTINUE Cluster error in Input error cluster Digital GPIB Address GPIB address of the Agilent 81680A tunable laser
7. 9 Drive Axis These three buttons provide manual control over stage motion The left ar row 4 initiates counterclockwise or negative direction motion The right arrow E gt likewise initiates clockwise or positive direction motion Clicking either arrow moves the selected Active Axis on the Active Stack a distance specified by the cor responding entry in the Step array The change in axis position will be updated in real time in the Position array The Stop button GQ halts any stage motion currently in progress Zero These buttons provide two different ways to zero the position of the selected Active Axis Clicking the Go button moves the Active Axis to the position 0 Clicking Set changes the label of the current Active Axis position to 0 Note that Set does not move the stage 24 Motion Control Drive Axis Confocal Smoothing Smoothing Filter Cutoff Smoothing Filter Rolloff Figure 9 The Motion Control control group Confocal Scanning Stage motion may be optionally accompanied by data acquisition to enable confocal scanning Generally confocal scanning is associated with motion along the Z axis but the software allows for data acquisition during motion of any axis Controls associated with confocal scanning are also located in the Motion Control area of the main user interface Confocal Toggles confocal data acquisition on and off When off no data acquisition occurs during stage motion When on data is acquire
8. As of this writing only the Precision Ranging method has been implemented Future methods may include Confocal and Peak Optimization Transverse Axis Selects the transverse motion axis Confocal Axis Selects the confocal scanning axis for the Confocal method not yet imple mented Peak Specifies the reflection peak configured in the Peak Selection and Measurements array that corresponds to the planar reflecting interface being perpendicularized Transverse Step Sets the transverse distance to move Tilt Angle Displays the measured tilt angle Measure Tilt Initiates a tilt angle measurement Adjust Angle Rotates the sample to compensate for the measured tilt angle This button is disabled until a tilt angle measurement has been performed 3 1 8 Scanning OFDR Measurements The Scanning OFDR software allows for measurements of reflection peak amplitude and range to be performed as a function of either one or two spatial coordinates by sequentially perform ing OFDR measurements and moving the Seruga Seiki stage axes Scanned measurements 29 Scanning Scan Type Axis 1 Settings Axis 2 Settings Axis Axis Steps Steps Direction Direction Current Step Current Step Figure 13 The Scanning control group return an amplitude value and a range value for each peak specified in the Peak Selection and Measurements array at each scan location To perform scanned OFDR measurement use the controls under the Scanning heading sele
9. Parameter settings in this VI must accurately correspond to the present hardware state in order for the Scanning OFDR system to operate without error 56 Called by Custom VIs called Edit Stage Limits vi Scanning OFDR 2 2 vi SS Toggle Software Limits vi SS Set Software Limit vi SS Set Remote Mode vi SS Query Status vi SS Query Software Limit vi SS Query Position vi OFDR Global vi Labview VIs called None LVClass Enum Boolean Boolean Boolean Cluster Boolean Digital Boolean Boolean Enum Boolean Boolean Inputs 12 Name Axis Current gt Hi Limit Current gt Low Limit Done error in Limits Enabled New Limit Postion Set High Limit Set Low Limit Stack Update Use Current Postion Outputs 4 Description Stage axis selection Set the high clockwise software limit to the current po sition Set the low counterclockwise software limit to the cur rent position Input error cluster Toggle software limits for the selected axis on and off Enter a value for a new software limit position setting Set the high clockwise software limit to the value of New Limit Position Set the low counterclockwise software limit to the value of New Limit Position Stage stack selection Update displayed position and limit values for selected stack and axis Specify whether to use the current axis position for a software limit setting 57 L
10. an internal shutter is closed and no light is output When disconnecting fiber from the laser be sure to deactivate the output using the button directly above the LED Reactivate the output once a fiber has been reconnected The Scanning OFDR software should generally remotely activate the output when needed but it is possible to run into errors because the laser output is off e Running the Scanning OFDR software puts the laser into Remote mode Pressing buttons on the laser will have no effect until it is returned to local mode which is accomplished by pressing the bottom softkey which is labeled Local when the laser is in Remote mode e The polarization of the laser output varies when the wavelength is swept To keep the laser polarization constant over wavelength the HP 8169A polarization controller is being used as a broadband polarizer This instrument includes a linear polarizer followed by a half waveplate and a quarter waveplate Because the light output by the laser is not guaranteed to be linearly polarized after traveling through a length of Tuning rate nm s 2 2 SE A T E o 8 D S c E 30 5 25 1 1 I 1 1 1 l 1 25 1 1 1 0 40 80 120 160 200 240 220 0 221 0 2220 2230 2240 225 0 Time ms Time ms Figure 2 Measured tuning rate for the Agilent 81680A tunable laser for a wavelength scan from 1520 nm to 1530 nm left and a 5 ms portion of the same scan showing the fine stru
11. recent measurement values used to calculate the mean value are the values present in the Amplitude Chart Amplitude Std Dev Indicates the standard deviation of the recent amplitude measure ments of the peak stored in the Amplitude Chart Ref Peak The reference peak used for the precision ranging calculation to precisely deter mine the range to the peak This control is a drop down list containing all currently configured peaks in the Peak Selection and Measurements array If None is selected the range is calculated relative to the reference arm of the OFDR interferometer If a reference peak is selected the range is calculated relative to the reference peak Range ps The range to the reflection peak calculated using the precision ranging algo rithm Strictly speaking this is the optical path delay to the peak in picoseconds Range Mean Indicates the mean of recent range measurements for the peak The recent measurement values used to calculate the mean value are the values present in the Range Chart Range Std Dev Indicates the standard deviation of the recent range measurements for the peak stored in the Range Chart X Removes the peak from the Peak Selection and Measurements array Performing Measurements Each time an externally clocked OFDR measurement is per formed the range measurements in the Peak Selection and Measurements array are updated based on the newly acquired data The amplitude measurements are also upda
12. Array Data In Complex midband data set input Outputs 1 LV Class Name Description Array Baseband data Complex data set shifted to baseband out VI description This VI shifts complex data to baseband by multiplying the phase by a pi per sample phase ramp Note that this VI also works in reverse If a baseband signal is input then the output is a midband signal Here baseband means a signal with a peak near the first element of it s discrete Fourier transformed data array while midband means a signal with a peak near the center of the discrete Fourier transformed data array 45 Buffer Points vi Called by Custom VIs called Scanning OFDR 2 2 vi OFDR Global vi Clock Source Enum ctl Labview VIs called None Inputs 6 LVClass Name Description Digital Clock Freq Hz Clock frequency for timed acquisitions Enum Clock Source Clock source for data acquisition see VI description Digital End Wavelength Requested sweep end wavelenth in nanometers nm Cluster error in no Input error cluster error Digital Start Wavelength Requested sweep start wavelenth in nanometers nm Digital Sweep Buffer Additional sweep bandwidth for wavelength calibration nm Outputs 3 LVClass Name Description Digital pts w buffer Number of data points in the data array prior to wave length calibration Cluster error out Output error cluster Digital requested pts Number of data points in the final data array not includ ing
13. B from the shortcut menu for more information about the error Clock mode for data acquisition see VI description The requested number of data points per channel to ac quire Description Data acquisition task name Output error cluster VI description This VI configures the data acquisition hardware in the OFDR system in preparation for acquiring measurement data Depending on the data acquisition 52 board being used different methods of triggering and clocking the data acquisition process may be supported The modes supported by this VI specified by Mode include format Sweep Ext Clock In this mode the acquisition looks for a start trigger on the pin specfied by the global variable Start Trig Pin and is clocked by an externally applied analog signal on pin PFIO Sweep Int Clock In this mode the acquisition looks for a start trigger on the pin spec fied by the global variable Start Trig Pin and is clocked by the internal clock on the data acquisition board Confocal In this mode the start trigger and acquisition clock are both derived by an externally applied digital signal applied to either of the pins specified by the global variables Stage CW Pulse Pin and Stage CCW Pulse Pin depending on the value of CW No Sweep SW trigger In this mode the acquisition does not look for an external start trigger and instead begins immediately The acquisition is clocked by the internal clock on the data acquisition
14. Dialog vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 2 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Outputs 2 LV Class Name Description Digital Drive Speed Current drive speed setting Cluster error out Output error cluster VI description Queries the drive speed setting for the specified Seruga Seiki stage axis 96 SS Query Position vi Called by Scanning OFDR 2 2 vi Set Postion Label vi SS Monitor vi Edit Stage Limits vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 2 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Outputs 2 LV Class Name Description Cluster error out Output error cluster Digital Position Value Current position VI description Queries the position ofthe specified Seruga Seiki stage axis 97 SS Query Software Limit vi Called by Set Postion Label vi Edit Stage Limits vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 3 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Boolean Hi Limit Specifies whether to query the clockwise limit True or the counterc
15. LabVIEW documen tation for Interpolate 1D vi for descriptions of the avail able methods Description The number of data points in the resampled output data array The reciprocal of the frequency spacing of the resampled data array The start wavelength of the resampled data array This may be slightly different that the start wavelength of the input data array depending on the interpolation method The resampled ouput data array VI description This VI interpolates time synchronously sampled wavelength sweep data onto a grid of equal frequency increments using a known frequency vs time relationship for the wavelength sweep This VI optionally performs a Fourier interpolation on the time sampled data prior to interpolation onto the frequency grid The frequency vs 81 time data array is assumed to be decending in frequency corresponding to wavelength sweeps from low to high wavelengths The time increment of the frequency vs time data array is not needed the data points only need to be separated by equal time intervals 82 Called by Custom VIs called Labview VIs called OpenG VIs called Save Configuration vi Save OFDR Config vi None TRef Get All FP References vi NI_LVConfig Ivlib Config Data RefNum ctl Write Key Variant __ogtk vi Inputs 4 LV Class Name Description Cluster error in no Input error cluster error TypedRefNum INI refnum Configuration file reference String Tag Descripti
16. Method element of the Tilt Cluster specifies how the range data was measured which affects the calculation code should interpret this data Currently only the Precision Ranging method has been implemented 49 Check Instruments vi Called by Scanning OFDR 2 2 vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 2 LVClass Name Description Cluster error in no Input error cluster error Boolean Show dialog Indicates whether to display a dialog window to the user if hardware is not found Outputs 2 LVClass Name Description Cluster error out Output error cluster String Message Status message VI description This VI checks for the presence of the Seruga Seiki stages and the Agilent 81680A tunable laser at the GPIB addresses specified in the global variables b Stage GPIB Addressj bj and jbj Laser GPIB Addressj bj 50 Called by Custom VIs called Confocal Plot Data vi Scanning OFDR 2 2 vi Smoothing Filter vi OFDR Global vi Labview VIs called None Inputs 5 LVClass Name Description Cluster error in no Input error cluster error Digital Filter Cutoff Smoothing filter bandwidth specification Digital Filter Roll Off Smoothing filter roll off specification Width Array Raw Data Data array containing raw confocal scanning data Boolean Smoothing Selects whether to apply a smoothing filter to the confocal data Outputs 2 LVClass Name Description Array Confocal Data Processed confocal scan d
17. Outputs 2 LVClass Name Cluster Error out TypedRefNum Queue Out Description Input error cluster Array of states to add to the queue Reference to the Communication Queue Indicates whether to add new states to the front or back of the queue or to replace states currently in the queue Description Output error cluster Reference to the Communication Queue VI description This VI manages the Communication Queue in the main Scan ning OFDR program 78 Queue Manager Proc vi Called by Scanning OFDR 2 2 vi Custom VIs called Processing States ctl Labview VIs called Clear Errors vi Inputs 4 LVClass Name Cluster Error in Array Q States TypedRefNum Queue In Enum Where Outputs 2 LVClass Name Cluster Error out TypedRefNum Queue Out Description Input error cluster Array of states to add to the queue Reference to the Data Processing Queue Indicates whether to add new states to the front or back of the queue or to replace states currently in the queue Description Output error cluster Reference to the Data Processing Queue VI description This VI manages the Data Processing Queue in the main Scan ning OFDR program 79 Called by Register User vi Custom VIs called None Labview VIs called None LVClass Boolean Cluster Boolean ComboBox LVClass Boolean Cluster Boolean String VIRefNum Inputs 4 Name Cancel error in no error Ok
18. Powered At CCW Mechanical Limit At CW Mechanical Limit Moving At CCW SW Limit At CW SW Limit Interrupted Axis Selected CCW SW Limit On CW SW Limit On 100 SS Select Axis vi Called by Scanning OFDR 2 2 vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 2 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Specifies the active axis selection on the Seruga Seiki D120 mo tion controller 101 SS Set Acceleration vi Called by Scanning OFDR 2 2 vi Stage Settings Dialog vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 3 LVClass Name Description Digital Acceleration Acceleration value Allowable values are 0 9999 String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Sets the acceleration value for the specified Seruga Seiki stage axis 102 Called by SS Set Distance vi Scanning OFDR 2 2 vi Stage Settings Dialog vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 3 LVClass Name Description String Axis Axis selection Allowable values ar
19. Seiki stages via GPIB communication The most commonly used stage settings are located to the right of the Peak Selection and Measurements array in the Seruga Seiki Stage Settings area This area includes the following controls and indicators Active Stack Selects the active Seruga Seiki stage stack Each stack comprises six axes of motion The physical stage stacks are labeled 1 and 2 Active Axis Selects the active stage axis Each stack has the following axes which are labeled on the hardware X Y Z Ox Oy and 0z Step This is an array of six step distances with one entry for each axis of the active stage stack Distances are in units of stage ticks where one tick is approximately equal to 40 nm Valid step sizes are in the range 0 8 000 000 Position This is an array of six current positions with one entry for each axis of the active stage stack Positions are also in units of ticks This array is an indicator only and cannot be used to set the axis positions see Driving the Stages below Each axis has three other settings that determine how each motion request is executed These settings are less commonly changed and are modified by selecting the menu option System Stage Settings This brings up the Seruga Seiki Stage Settings dialog window shown in Fig 8 This dialog window has the following controls Active Stack Has the same function as Active Stack in the Seruga Seiki Stage Settings area of the main user interfac
20. Stage vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 3 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Digital Position Position to move the selected axis to Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Moves the selected Seruga Seiki stage axis to the specified po sition Positions are specified in stage units ticks of approximately 40 nm Allowable position values are in the range 8000000 to 8000000 92 Called by Custom VIs called SS Monitor vi Move SS Stage vi Stage Setting Array ctl SS Stop vi SS Query Status vi SS Query Position vi Axis Selector ctl Labview VIs called None Inputs 5 LVClass Name Enum Active Axis String Axis Cluster error in Array Position Boolean Stop Outputs 6 LVClass Name Boolean At Limit Boolean Axis powered Cluster error out Boolean Interrupted Boolean Moving Array Position out Description Stage axis selection for updating software controls Axis selection for hardware communication Allowable values are Al A6 for stage stack 1 or A7 A12 for stage stack 2 Input error cluster Stage axis position array Optionally stop current motion Description Indicate if axis is at a limit Indicates if axis is powered Output error cluster Indicate if prior axis
21. String used to begin filenames for autosaved OFDR data VI description This VI presents a dialog interface to the user to configure op tions for automatically saving raw OFDR data whenever wavelength sweeps are performed When autosaving is enabled data is saved using filenames that begin with Filename Root followed by a timestamp 85 Save Scan Data Dialog vi Called by Scanning OFDR 2 2 vi Custom VIs called Save Scan Cluster ctl Labview VIs called Write To Spreadsheet File vi Write To Spreadsheet File DBL vi Inputs 7 LVClass Name Description Boolean Append Timestamp Select whether to append a timestamp to filenames Array Array Array of clusters of data save parameters see VI descrip tion Boolean Cancel Discard changes and close the dialog window Cluster error in no Input error cluster error Path Folder Path Select the destination folder for saved data Boolean OK Accept changes and close the dialog window DataValRefNum scan data value Data value reference to scanned OFDR data reference Outputs 3 LV Class Name Description Boolean Canceled Indicates whether the user canceled the operation Cluster error out Output error cluster Path Folder Path Out The destination folder for saved data VI description This VI presents a dialog interface to the user to configure op tions for saving scanned OFDR data The Array of data save parameters will contain one element for each peak that has been con
22. System System Parameters This brings up the Edit Hardware Parameters dialog window shown in Fig 6 For most general usage scenarios these parameters will not change If values do not correctly reflect the current harware configuration however the system will not function DAQ Board Two data acquisition boards are currently available the PCI 6115 which 16 r 7 13 Edit Hardware Parameters vi pa Edit Hardware Parameters Laser GPIB Address DAQ Board Stage GPIB Address Trigger Delay ns Trigger Hysteresis V Channel Signal Input High Low Assignment Name Coupling Limit V Limit V Cancel Figure 6 The Edit Hardware Parameters dialog window resides inside the HP workstation and is accessed by the BNC 2110 connector block and the PXIe 4492 which resides in the PXIe 1073 chassis Generally the PCI 6115 should be used The PXIe 4492 does not support all system features Laser GPIB Address This value should be 19 unless changed on the Agilent 8164A main frame Stage GPIB Address This value should be 7 unless changed on the Seruga Seiki D120 motion controller Trigger Delay ns This value is the relative delay between the two arms of the trigger interferometer in the OFDR optical network If the current trigger interferometer delay is not known measure the delay using Calibrate Interferometer v2 vi Trigger Hysteresis V This is the hysteresis value when using an external analog clock signal
23. The E Tek fiber optic switch in the reference arm allows the reference arm to be opened partially mitigating coherent effects when performing confocal scans The switch is driven by a 5V pulse on the ctr0 and ctrl outputs of the PCI 6115 DAQ board The pinout for the switch is shown in Fig 4 The switch is not mounted in a PCB so the physical connection to the switch is made via test clips The switch pins are fragile and the switch is expensive to replace so the switch pins are run through a header Digi Key part number A100205 ND The OFDR interferometer uses a three coupler geometry with a transmissive reference arm and a reflective test arm Currently the test arm has three probe paths each with a different delay allowing their contributions to be separated from one another in the OFDR time domain data sets Two probes have antireflection coated FC PC connectors at their output The third is a bare fiber that may be spliced to a device under test Signal Detection and Acquisition The optical signals on the S P Aux and Frequency Clock channels are currently de tected using Thorlabs PDA10CS amplified photodetectors The HCN signal is detected using an older roughly equivalent model These detectors have adjustable gain and their bandwidth varies inversely with the gain setting The gain settings and associated bandwidths are summarized in Table 2 Two different DAQ boards are available for use a PCI 6115 and a PXIe 4492 both manufac
24. e Raa aa 66 Loe Manage Ni 4025544 cak e a ede bee Pee A e bas 67 Measurement Options Dialog vi 0 2 20002 eee 68 Move SO Staged v sT gu de once Bo Skee eo Fos ee We ae ee 69 OFDR Global lt ac 4428 425 42a a EERE EAE ERS AER EO 70 OFDR Plot Data Vi e 24 aes ee bre hae heh aw de hehe Sadan 72 P ak Amplitudes yii ie Ye oe a He oe WA EERE Ba wR Ee aS 73 Peak Optimizer Vi av a ae ace a RG a de ee a de la em 75 Precision Ranging2 Vi e se sms e Re eee ek ee 76 Queue Manager Comm yi sau ceeds pee SR oe ee RR ees 78 Queue Manager Proc Vi crisis rra dee oo 79 Register User ocio a Se ee BAR oe fe Hw ee Mek w ae Ph 2 ee 80 ResampleVi 3 sei 564 e224 26 5 beg bee ERG R EE ERE DE AD Re 81 Save Configuration Vie s s ee ee ke soa g ee a 83 Save OFDR COMIS YL 4 5 Sa ae w ar m ee ER Ee oe eee a 84 Save Options Dialog Vi ce e sa e sacie o e a e a ee eee 85 Save Scan Data Dialog Vi a saoe opoe a ee a 86 Scan Managen yi s Vga ar ai a aie a Sok ack O 87 Set Postion Label Vi 224 4 2 G0 a a eG ee we a ee 88 Signal Leyels vi o e co 454 2 42 4 0008 a bebe eG ae Eee Ap EE 89 Smoothing Filter Vie e s sa 22 oboe wb ane Mee eee Oe eee bee 90 SS Drive AXIS Vi 4445 4 444 ASS Be ee Rw Ce a Bae ae ae BOS 91 SS Go To Positional 40 a gow eee a Bee eH os EO gk d ae Aione ee 92 SS Monitor Vi a oe sa 644 285 425 b had bE ERR ERE CRSA DRO 93 SS Query Acceleration vi e 94 SS Query Distante Vi e se e Yow ae a
25. fea ee Gok A ee we AER wk ee Agilent Cycle Number Vie e seem eor mad ee Agilent Laser On Off vi aaaea ee Apilent Power los a a oae pa Ge ii ee a ee Agilent Query Sweep State vi 2 a a ee Agilent Start Wavelength vi 2 0 0 0 0 2 00 eee ee eee Agilent Startup Sequence Vi e Agilent Stop Wavelength vi 0 0 020 002 10 12 12 Agilent Sweep Actions vi ee 42 Avilent Sweep Models dates s Ak de ee EO koh ee ee 43 Agilent Sweep Speed vi 2 2 ee 44 basebandlaYl pls 2o04 ose ee ke ew ED a ee 45 Butter Points Vi meut a e be aoe ee a a Od Ee we ee eS 46 Calculate tsi e una ata he Gow ad te ee de eh Re A Bee lia 48 Check Instruments Vie ao inside 50 Confocal Plot Data yi sor ss sa sopra os bow Boe Sd a Oe aces Soe we 51 DAQ Come V3 Vi e ow a e yA alee a Pa a a ee i 52 DAQ Read Vi 22 42 h4 22344 ra a aa 54 DriveOpticalSwitchvi taat ea ee 55 Edit Hardware Parameters vi eai a a ee 56 Edit Stage Lamitsiva os guk dac once al ee e e esos Ee Hoek d ae a E i 57 Enqueue Config States vi lt oe so eeds ma Cana aad ena cta Goran 59 Enqueue Tilt Measurement vi aoaaa a a 60 Fourier Interpolation vi s s saena a sees eio ahi i iak ee 61 Generate XASISVL soaa a a g aioi a A a e a a Re a 62 Get Channel Assignments vi ooo e e a 63 Handle Peak Array Vi ee ee 64 Load Configuration s s a s r e a e eee A A ee ke e 65 Load OFDR Config Vi 244424444 eaoin anaia
26. on the front panel of the main OFDR program interface VIRefNum VI reference Reference to the VI whose configuration is being saved Outputs 2 LV Class Name Description Cluster error out Output error cluster VIRefNum VI reference out Reference to the VI whose configuration is being saved VI description This VI accepts a reference to the main OFDR VI and saves controls in both that VI and OFDR Global vi tagged with OFDRConfig in their descrip tions to a configuration ini file Also takes a reference to the main graph in the main OFDR VI so that cursor information can also be saved to the configuration file 84 Save Options Dialog vi Scanning OFDR 2 2 vi Called by Custom VIs called None Labview VIs called None Inputs 5 LVClass Name Path Autosave Data Folder Boolean Autosave Raw Data Boolean Cancel String Filename Root Boolean OK Outputs 4 LVClass Name Path Autosave Data Folder out Boolean Autosave Raw Data out Boolean Canceled String Filename Root out Description Specifies the folder where autosaved OFDR data is stored Toggles autosaving of OFDR data on and off Discard changes and close the dialog window String used to begin filenames for autosaved OFDR data Accept changes and close the dialog window Description The folder where autosaved OFDR data is stored Indicates whether autosaving of OFDR data is enabled or disabled Indicates whether the user canceled the operation
27. the sweep buffer for wavelength calibration VI description This VI determines the number of data points to acquire during a laser wavelength sweep This VI an additional sweep buffer for wavelength calibration but this calibration has not been implemented in the Scanning OFDR software The number of data points depends on both the sweep range start and end wavelengths and the type of clock used for acquisition For internal clock aquisitions the number of data points depends on the tuning rate of the laser and the clock frequency For external clock 46 acquisitions the external clock is assumed to be an interferometer with a fixed path length difference In this case the number of points depends on the interferometer delay which is stored in the global variable TrigDelay 47 Called by Custom VIs called Calculate Tilt vi Scanning OFDR 2 2 vi Tilt cluster ctl Processing States ctl OFDR Global vi Labview VIs called None Inputs 4 LVClass Name Description LV Variant Data A Tilt Cluster typedef cast as a variant see VI descrip tion Cluster error in Input error cluster Digital Notifier Code Code to indicate if distance data is ready A value of 2 indicates new precision ranging data Digital Range The measured distance to the sample surface Outputs 4 LVClass Name Description Boolean Done Indicates whether the tilt calculation is complete Cluster error out Output error cluster Array Queue States Queue st
28. vee A ee ae VS Se al a e 95 SS Query Drive Speed vi 2 a 96 So Query Position Vii 44 4 eos i446 be oe ho ba et Caled amp as 97 SS Query Software Limit vi e 98 SS Query Start Up Speed Vie ross o a a eS 99 SS Query Status Vi 2 se 5 4 84 44 Bee eS aaa a Se A 100 SS Select AXIS Vi 4 44064 26d e pede ed ow Pee bee De ee bee 101 SS Set Acceleration vi i c ca sr e poea lt ee ee ee 102 So Set DISTamceVi emplea FS Hoe ee RE ee 103 SS Set Drive Speed vi 2 104 SS Set Position Value vi gt iaoe saog o k ee 105 SS Set Remote Mode vi e 106 So pet Software Limit Vi sa cross a da a A e Ee 107 SS Set Start Up Speed vi s ees ee eRe ee eee eR wd 108 A Vim ae ete ge O Gece fom of a dee Gece ee ae ar 109 SS Toggle Motor Power vi e so caocca e area e eee ee ee 110 SS Toggle Software Limiits Vi sacs pois ucs w p sieb Wii eiie E Ses 111 Stage Settings Dialog Vi o e danau a eee 112 Sweep Agilent Laser 2 Vi e 114 Sweep Mer Q Cleamup Vi pea 0 0202 ee eee 115 Update End WENI es a ma s aces a RG ek ab ee Ae we Bo 116 Update Scan Data Vis s sanpo 4 SES eB eRe eh ne eR ae Gee 117 Wavelength Range vi 2 eara ee 119 WhLovs Time cias a e PO ade A E we BR ee 120 1 Introduction This document is intended to be a user s guide for the Scanning Optical Frequency Do main Reflectometer OFDR located in the McLeod Labs in the Department of Electrical
29. wheter or not the available disk space will be adequate Indicates the mean raw data value on the Aux channel Toggle averaging of wavelength sweep data on and off Not yet implemented Specifies whether averaging of multiple wavelength sweeps should be performed in the time domain or the frequency domain Not yet implemented Specifies the clock frequency when the Internal option is selected for Clock Source For the PCI 6115 DAQ board the maximum clock frequency is 10 MHz For the PXIe 4492 DAQ board the maximum clock frequency is 204 8 kHz Specifies the clock source for data acquisition during wavelength sweeps Internal uses the internal clock on board the data acquisition board External uses the ana log signal applied to PFIO on the data acquisition board Under normal usage this signal should be signal output by the trigger interferometer in the OFDR optical net work The PXIe 4492 DAQ board does not support ex ternal clocking so the Internal option must be used with this board The PCI 6115 DAQ board supports both in ternal and external clocking Enables or disables continuous wavelength sweeping This indicator displays the number of data points to be acquired for a wavelength sweep based on current sweep parameter settings OFDRConfig This is an OFDR configuration parameter stored in configuration files The number of data points neglected at each end of the filtered data set when performing curve fitting
30. 1528 1562 100 Torr H CN wavelength ref erence Its absorption spectrum is shown in Fig 3 Table 1 lists the wavelengths of the absorption lines The primary function of the gas cell is for calibrating the rela tive delay between paths in fiber interferometers In particular the OFDR relies on accurate calibration of the trigger interferometer delay often referred to as simply the trigger delay The gas cell may also be used for improving the wavelength accuracy of R Branch P Branch 20 20 Transmission a u 1530 1535 1540 1545 1550 1555 1560 Wavelength nm Figure 3 The absorption spectrum of the dBm Optics model WA 1528 1562 100Torr H13CN wavelength reference showing the absorption line numbering scheme swept wavelength measurements though this feature has not yet been implemented in the Scanning OFDR software e The connectors on the front of the Thorlabs box tend to spin When connecting or disconnecting them reach inside the box and hold the connector on the back side while twisting to ensure a good connection e The A and B outputs of the Thorlabs box allow for different trigger interferometer delays to be used by connecting different lengths of fiber The internal fiber lengths are approximately matched that is if the internal connectors at A and B are connected to one another the relative delay between the interferometer paths is approximately zero There is a manual polarization controller P
31. C2 that is meant to be included inline with the trigger interferometer delay line Adjust the polarization controller to maximize the fringe visibility of the frequency clock signal e To view the frequency clock signal temporarily disconnect the frequency clock BNC cable from the clock input on the data acquisition DAQ board and connect it to one of the analog input channels see Data Acquisition notes below Then use the Scanning OFDR software to perform an internally clocked acquisition see Sec 3 1 2 Alterna tively look at the frequency clock signal using an oscilloscope If using an oscilloscope remember that the laser must be sweeping when the clock signal is acquired e The OFDR interferometer uses polarization diverse detection at the output This de tection method avoids reduction in signal levels due to polarization fading To work properly this method requires that the light traveling through the reference arm of the interferometer the arm containing the switch in Fig 1 be polarized such that it is split evenly by the polarization beam splitter PBS at the output of the interferometer Ad just the manual polarization controller labeled PC1 to achieve an equal splitting ratio Table 1 Absorption line wavelengths for the dBm Optics model WA 1528 1562 100 Torr H CN wavelength reference Accuracy is 0 3pm except for wavelengths marked with an asterisk which are known to 0 6 pm R Branch P Branch Line no W
32. Computer and Energy Engineering at the University of Colorado at Boulder As such no theoretical background on the physics underlying the OFDR is provided here since that in formation is available elsewhere Rather this document provides an overview of the hardware configuration and a guide to the use of the system control software 2 Hardware The hardware layout of the Scanning OFDR is illustrated in Fig 1 The main components of the system are A tunable laser source specifically an Agilent 81680A tunable laser source e A fiber optic network the central feature of which is a fiber interferometer e Means for detecting and digitizing the optical signals output by the fiber optic network A set of precision motion stages for positioning and positional scanning of test samples A personal computer running the Scanning OFDR software application for controlling system hardware and performing data processing tasks This section will provide a series of hardware notes roughly organized according to this bulleted list of subsystems These notes are meant to record as many things you should know regarding the current hardware configuration for both users of the system and for system maintenance and modification in the future 2 1 The Agilent 81680A Tunable Laser e When the laser is rebooted it starts in a locked state The code to unlock the laser is 1234 e The laser has two optical outputs Output 1 is a low noise
33. Labview VIs called Log Manager vi Scanning OFDR 2 2 vi Enqueue Tilt Measurement vi Move SS Stage vi None Space Constant vi Inputs 5 LVClass Name Description Boolean Append Select whether to append timestamp to log entry timestamp T Boolean Clear Select whether to clear the log Cluster error in no Input error cluster error LVObjectRefNum Log Ref Reference to status log string control String New line New line to add to the status log Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description This VI manages the Status Log in the main Scanning OFDR program 67 Called by Measurement Options Dialog vi Custom VIs called None Labview VIs called None LVClass Boolean Digital Digital Boolean Digital LVClass Boolean Digital Digital Digital Inputs 5 Name Cancel Endpoints to Neglect Filter Size OK Peak Area Points Outputs 4 Name Canceled Endpoints to Neglect Filter Size Peak Area Points Scanning OFDR 2 2 vi Description Discard changes and close the dialog window Number of endpoints to neglect during precision ranging linear curve fit Number of points used for the precision ranging digital filter Accept changes and close the dialog window Number of points used for peak amplitude calculation Description Indicate whether or not the user canceled the operation Number
34. McLEOD RESEARCH GROUP UNIVERSITY OF COLORADO DEPARTMENT OF ELECTRICAL COMPUTER AND ENERGY ENGINEERING Scanning Optical Frequency Domain Reflectometer System Documentation Author Eric D Moore Document version 0 1 May 30 2012 This material is based upon work supported by the National Science Foundation under Grant ITP 1059286 to the American Society for Engineering Education Contents 1 Introduction 2 Hardware 2 1 2 2 2 3 2 4 2 5 3 1 3 2 The Agilent 81680A Tunable Laser 2 0 0 a eee The OFDR Fiber Optic Network o e e e Signal Detection and Acquisition 2 00000024 ee The Seruga Seiki Stage Systemi e The Control Computer s s s as s o 0845 4 04 baba ee ba eR As Software WSAGE os biG a ck me a ee Be Sy eS RS a dk he BG So Be ce 3 1 1 System Conligurabiol 246 44 6542 whee dae Hae a ay Bas 3 1 2 Performing Swept Wavelength Measurements 31 3 Displaying OFDR Data sonia o gt see e e ee ee 3 1 4 Peak Selection and Measurements 0 3 1 5 Motion Control s sacs eat ea tw Bae ane a 3 16 Peak Optimization so lt ao s pom sai be anioe moi e ee eS 3 1 7 Sample Perpendicularization si lt a s e roce as epe d Ena eee 3 1 8 Scanning OFDR Measurements a e 3 1 9 Savine Data p b bee bab hane o h ank ae a a h A a aa 3 1 10 Saving and Loading System Configuration SUBV I Listing gt sos eae a Pace
35. Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description This VI stops starts pauses or continues a wavelength sweep using the Agilent 81680A tunable laser 42 Agilent Sweep Mode vi Called by Agilent Startup Sequence vi Custom VIs called None Labview VIs called None Inputs 3 LVClass Name Description Cluster error in Input error cluster Digital GPIB Address GPIB address of the Agilent 81680A tunable laser ComboBox Sweep Mode Requested sweep mode Allowable values are STEPPED MANUAL and CONTINUOUS Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description This VI sets the sweep mode for the Agilent 81680A tunable laser The OFDR system only uses the CONTINUOUS sweep mode 43 Agilent Sweep Speed vi Called by Agilent Startup Sequence vi Custom VIs called None Labview VIs called None Inputs 3 LVClass Name Description Cluster error in Input error cluster Digital GPIB Address GPIB address of the Agilent 81680A tunable laser ComboBox Sweep Speed Requested tuning rate Allowable values are 0 5NM S 5NM S and 40NM S Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description This VI sets the sweep speed or tuning rate of the Agilent 81680A tunable laser 44 baseband2 vi Called by Precision Ranging2 vi Custom VIs called None Labview VIs called None Inputs 1 LV Class Name Description
36. R VI The raw wavelength sweep data array Reciprocal of the frequency spacing of the OFDR data set Description Output error cluster Output Peak Selection and Measurements array with up dated precision ranging measurement values The data points used for each precision ranging calcula tion The frequency domain phases of each filtered data subset VI description This VI performs data processing on raw OFDR scan data to 76 precisely locate reflection peaks to within a small fraction of the range resolution of the system Peak locations within the OFDR time domain data set are passed via the Peaks Array which is an array of clusters of the same type as the Peak Selection and Measurements array on the front panel of the main Scanning OFDR software application The precision ranging calculation consists of selecting a number of points given by Filter Size Pts from the OFDR time domain data array around the location of each peak These data subsets are inverse Fourer transformed and the resulting frequency domain phases are shifted to baseband and then fit to a line The slope of the line determines the reflector location to within a small fraction of the time domain sampling interval 77 Queue Manager Comm vi Called by Scanning OFDR 2 2 vi Custom VIs called Communication States ctl Labview VIs called Clear Errors vi Inputs 4 LVClass Name Cluster Error in Array Q States TypedRefNum Queue In Enum Where
37. Step Scan settings cluster output with updated Current Step Output error cluster Queue state array VI description This VI manages scanning OFDR measurement using the Seruga Sekei stages It enqueues states to be called in the main Scanning OFDR program that perform swept wavelength measurements and stage motion It is meant to be called in a loop where each call performs a single OFDR measurement and determines the next stage movement if any 87 Set Postion Label vi Called by Scanning OFDR 2 2 vi Custom VIs called Stage Setting Array ctl SS Set Software Limit vi SS Set Position Value vi SS Query Software Limit vi SS Query Position vi OFDR Global vi Axis Selector ctl Active Stack Enum ctl Labview VIs called None Inputs 6 LVClass Name Enum Active Axis Enum Active Stack Cluster error in Digital New Position Label Array Position Boolean Shift limits Outputs 3 LVClass Name Cluster error out String Message Array Position out Description Stage axis selection Stage stack selection Input error cluster New position label setting Stage axis position array Indicates whether or not to shift axis software limits Description Output error cluster Message for status log Stage axis position array VI description This VI sets the position label for the selected Seruga Seiki stage axis to a new value Note that this VI does not move the stage but only changes the label val
38. VClass Digital Cluster Digital Digital Name Current Position error out High Limit Low Limit Description Current position of the selected axis Output error cluster High clockwise software limit setting for the selected axis Low counterclockwise software limit setting for the se lected axis VI description This VI is a dialog user interface for setting the software limits for the Seruga Seiki stages 58 Called by Custom VIs called Enqueue Config States vi Scanning OFDR 2 2 vi Stage Settings Cluster ctl Stage Setting Array ctl Stage Parameter ctl Processing States ctl Communication States ctl Active Stack Enum ctl Labview VIs called None Inputs 4 LVClass Name Description TypedRefNum Comm Queue Reference to the Hardware Communication Queue Cluster error in no Input error cluster error TypedRefNum Proc Queue Reference to the Data Processing Queue Cluster Value Cluster Cluster of configuration values see VI description Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description This VI queues the states necessary to update the state of the hardware and software after loading a configuration file Value Cluster contains values read from the configuration file that are required to be passed to the various states in the queues 59 Enqueue Tilt Measurement vi Called by Scanning OFDR 2 2 vi Custom VIs called Tilt cluster ctl S
39. VIs called None Inputs 3 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Digital Start Up Speed Start up speed value Allowable values are 10 9999 Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Sets the start up speed value for the specified Seruga Seiki stage axis 108 SS Stop vi Called by SS Monitor vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 1 LVClass Name Description Cluster error in Input error cluster Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Stops a Seruga Seiki stage axis currently in motion Note that the axis does not stop instantly but rather decelerates smoothly to a stop 109 SS Toggle Motor Power vi Called by Scanning OFDR 2 2 vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 3 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Boolean Motor On Off Motor power setting True On False Off Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Toggles the power to individual Seruga Seiki stage axes Motor power must be on before controlling axes remotely When motor power is off th
40. able values are 1 100 Cycles Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description This VI sets the number of consecutive wavelength sweeps the Agilent 81680A tunable laser will perform 35 Agilent Laser On Off vi Called by Sweep Agilent Laser 2 vi Agilent Startup Sequence vi Custom VIs called None Labview VIs called None Inputs 3 LVClass Name Description Cluster Error In Input error cluster Digital GPIB Address GPIB address of the Agilent 81680A tunable laser Boolean Laser On Off Requested optical output state True On False Off Outputs 2 LVClass Name Description Cluster Error Out Output error cluster Boolean Output Requested optical output state True On False Off VI description This VI toggles the optical output of the Agilent 81680A tunable laser on and off 36 Agilent Power vi Called by Scanning OFDR 2 2 vi Agilent Startup Sequence vi Custom VIs called None Labview VIs called None Inputs 3 LVClass Name Description Cluster error in Input error cluster Digital GPIB Address GPIB address of the Agilent 81680A tunable laser Default 19 Digital Power mW Requested power setting in mW Outputs 2 LVClass Name Description Cluster error out Output error cluster Digital Output Power Requested power setting in mW mW VI description This VI sets the output power level of the Agilent 81680A tun able laser 37 Agilent Query Sweep State vi
41. abled Update Use Current Position Set High Limit New Limit Postion Set Low Limit E Figure 10 The SS Stage Software Limits dialog window Axis Selects the active stage axis Software Limits Enabled Enables or disables software limits for the selected axis The upper right portion of the dialog window contains three indicators and a button control Current Position The current position of the active stage axis High Limit The current high software limit setting for the active stage axis Low Limit The current low software limit setting for the active stage axis Update Updates the above three indicators The central region of the dialog window contains the controls for setting new software limit values New Limit Position The position value to use for the new software limit Use Current Position When checked New Limit Position is set to the current position of the active axis If New Limit Position is changed to a different value Use Current Position becomes unchecked Set High Limit Sets the upper software limit for the active axis to the value of New Limit Position Set Low Limit Sets the lower software limit for the active axis to the value of New Limit Position Because software limits are specified in the stage axis coordinate system changing the zero location of this coordinate system causes a shift in the physical location of the software limits The Scanning OFDR software will optionally shift the s
42. aded model at some point A full length PCI slot is required to accommodate the PCI 6115 DAQ board The MXI interface to the PXle 1073 chassis requires a PCI Express x1 slot The Scanning OFDR software is written in the 64 bit version of LabVIEW 2011 3The mating connector type is specified as DX40 20P in the D120 Series Stepping Motor Controller In struction Manual and Digi Key carries a DX40M 20P which doesn t quite fit 12 483 Scanning OFDR 22 vi cas al File Edit System Developer Help m gt O P Ploto N Swept Wavelength Acquisition Start Wavelength End Wavelength Plot Selection Laser Power mW Hea Clock Source Clock Freq Hz Data Buffer Size Number of Sweeps Averaging Domain Averaging Window S Mean P Mean Aux Mean Continuous o 7 T 7 T 7 T C 3 46433 3 3 35 351 Sweep D Time ns Peak Selection and Measurements Motion Control Amplitude Mean Std Dev Ref Peak Range ps Mean Drive Axis Peak Pickup Location a dd Position Zero Peak Pickup Location Confocal Pickup Loci A Smoothing Pickup Recalculate Refresh Cursor List lt W gt Server localhost Figure 5 The graphical user interface for the Scanning OFDR system software 3 Software The Scanning OFDR system software is written in National Instruments LabVIEW 2011 As of this writing the most recent version of main user interface and source code framework is found in the file Scanning OFDR 2 2 v
43. ain plot area Note this parameter is not stored in configuration files The reason is because its allowable values depend on what type of measurement was most recently performed wavelength sweep or confocal scan and loading a con figuration file does not affect the raw data in memory Indicates the current position for each axis of the Seruga Seiki stage stack specified by Active Stack Positions are in terms of ticks where 1 tick is approximately equal to 40 nm Recalculate the amplitude and precision ranging measure ment values in the Peak Selection and Measurements array Perform this recalculation after modifying peak lo cations within the array Indicates the mean raw data value on the S channel During ordinary operation polarization controller PC1 should be adjusted so that S Mean and P Mean are equal Indicates whether or not the software limits of the ac tive stage axis should be shifted when the zero location is changed This control is disabled toggle this option using the menu option System Shift Limits with Zero Specifies the starting wavelength for wavelength sweeps 15 LVClass Array TabControl Boolean Digital Boolean Boolean String Enum 3 1 Usage Table 4 User interface control descriptions continued Name Step SupPlotsTab Sweep Sweep Buffer nm Update Cursor List Use 27n User Window 3 1 1 System Configuration Description Indicates and s
44. ak Optimization heading selection in the lower right region of the Scanning OFDR user interface This set of controls is shown in Fig 11 Peak Set the peak to optimize This value refers to the Peak of a peak that has been configured in the Peak Selection and Measurements array Optimize Peak Initiates the peak optimization process The peak optimization process 27 Peak Optimization lt lt Select active axis and step size Peak Optimize Peak Abort Figure 11 The Peak Optimization control group incrementally moves Active Axis by the value of the corresponding element of Step The amplitude of the peak specified by Peak is monitored and motion continues as long as the amplitude of the peak increases If the amplitude decreases for motion in one direction the other direction is tried Once the peak amplitude decreased for motion in both directions the axis position is returned to the location of the maximum peak amplitude and the peak optimization routine terminates Abort Aborts the peak optimization process 3 1 7 Sample Perpendicularization A common measurement performed using the Scanning OFDR is a spatially resolved mea surement of reflectivity for a planar sample under test as a function of transverse position Because of the confocal filtering effect of the single mode fiber core discussed above it is important that the planar interface remain at the focal position of the probe beam as its position is scan
45. ard Use of the External clock option with the PXIe 4492 DAQ board will result in an error because the PXIe 4492 DAQ board does not support external clocking 18 4 If Clock Source is set to Internal then set the desired Clock Freq Hz When using the PCI 6115 DAQ board the maximum clock frequency is 10 MHz When using the PXIe 4492 the maximum clock frequency is 204 8 kHz If Clock Source is set to External the value of Clock Freq Hz is ignored 5 Select the desired Number of Sweeps This is the number of consecutive wavelength sweeps that will be performed when the Sweep button is clicked 6 Click the Sweep button to perform the wavelength sweep and acquire data 7 After sweeping note the values of the S Mean and P Mean indicators These values should be approximately equal within 5 If this is not the case adjust the polariza tion controller PC1 while performing additional sweeps to equalize these values This process ensures that the polarization diverse detection channels are balanced 4 Continuous Sweeping To continuously sweep and acquire data click the Continuous checkbox When the Continuous checkbox is checked the Sweep button will remain de pressed after clicking and the laser will continuously sweep and acquire data To stop contin uous sweeping click the the Sweep button again it s label changes to Sweeping while data acquisition is in progress or uncheck the Continuous checkbox 3 1 3 Displaying OFDR Data
46. array on the front panel of the main Scanning OFDR software application The Scan Data array is a three dimensional array Each selected peak is as sociated with two adjacent pages in the array in the order of peak number The first of these two pages is for amplitude data and the second is for range data Within each page rows and columns correspond to locations within a 2D scan Rows correspond to steps along Axis 1 and columns correspond to steps along Axis 2 For 1D scans each page is still a 2D 117 data array structure but with only one row Each time an OFDR measurement completes during a scan this VI places the resulting amplitude and range values at the correct data locations within the Scan Data array If multiple wavelength sweeps are requested at each scan location data stored in the Amplitude Chart and Range Chart on the front panel of the main Scanning OFDR software application is used for averaging This VI could be made more memory efficient by passing the Scan Data data value reference rather than the Scan Data array 118 Wavelength Range vi Called by Update End WL vi Custom VIs called None Labview VIs called None Inputs 3 LVClass Name Description Digital of Ranges The number of sweep ranges requested Digital Start Wavelength Wavelength sweep start wavelength nm Digital Trigger Delay Trigger interferometer delay reciprocal of the frequency ns spacing of wavelength sweep data Outputs 2 LVClass Nam
47. ata Cluster error out Output error cluster VI description This VI processes raw confocal scan data for display in the main graph on the front panel of the Scanning OFDR software application Specifically it combines data from the S and P channels and optionally applies a smoothing filter See Smoothing Filter vi for a description of the filter ol Called by Custom VIs called Labview VIs called LVClass Digital Boolean Cluster Enum Digital DAQ Config v3 vi Scanning OFDR 2 2 vi OFDR Global vi DAQmx Timing vi DAQmx Timing Sample Clock vi DAQmx Start Task vi DAQmx Create Virtual Channel vi DAQmx Create Task vi DAQmx Create Channel Al Voltage Basic vi DAQmx Clear Task vi Clear Errors vi Inputs 5 Name Clock Frequency Ez CW error in no error Mode Requested Sample Points Outputs 2 LVClass DAQmxName Cluster Name DAQmx Sweep Capture Task error out Description Clock speed for time synchronous acquisitions Maximum values are 10MHz for the PCI 6115 and 204 8kHz for the PXTe 4492 Direction specifier for confocal scanning acquisitions B error in B can accept error information wired from VIs previously called Use this information to decide if any functionality should be bypassed in the event of errors from other VIs Right click the B error in B control on the front panel and select B Explain Error B or B Explain Warn ing
48. ate array This is either empty or contains the CalcTilt state if more data is still required Digital Tilt angle The calculated tilt angle of the sample under test If the calculation is incomplete this returns a value of 360 VI description This VI performs data recording and calculation functions for measuing the tilt of a sample under test It is intended to be called in a data processing loop during while the data for the tilt measurement is being acquired This VI should be called once per distance measurement The tilt measurement requires two distance range measurements at two different transverse locations of the sample under test Because both hardware communication and data processing states must execute before the correct data is present in memory for the tilt measurement the CalcTilt state in the main Scanning OFDR program waits for a notifier before calling this VI The notifier is used for other syncronization tasks as well this VI checks the notification code to determine whether it should proceed 48 with the tilt calculation or if it should wait If it should wait it just enqueues the CalcTilt state again If the notifier indicates data is present it stores the first range value in the FirstPos element of the Tilt Cluster and increments the counter NumPos When the second distance value is ready it calculates the tilt using the difference in ranges and the Transvere Step value passed via the Tilt Cluster The
49. avelength nm Line no Wavelength nm 25 1528 0541 1 1543 1148 24 1528 4862 2 1543 8094 23 1528 9271 3 1544 5147 22 1529 3762 4 1545 2314 21 1529 8376 5 1545 9563 20 1530 3061 6 1546 6902 19 1530 7856 7 1547 4354 18 1531 2764 8 1548 1904 17 1531 7738 9 1548 9554 16 1532 2825 10 1549 7302 15 1532 8024 11 1550 5149 14 1533 3291 12 1551 3106 13 1533 8671 13 1552 1157 12 1534 4159 14 1552 9308 11 1534 9723 15 1553 7560 10 1535 5401 16 1554 5892 9 1536 1170 17 1555 4346 8 1536 7034 18 1556 2919 7 1537 2997 19 1557 1573 6 1537 9069 20 1558 0329 5 1538 5224 21 1558 9185 4 1539 1494 22 1559 8143 3 1539 7855 23 1560 7185 2 1540 4314 24 1561 6344 1 1541 0872 25 1562 5625 0 1541 7529 2 3 2 White dee od 2 7 eee o Pin connection and status Pin status Optical Path Electrical drive Status contacts l 12 2 E 12113 IE SIS Reflection 1 3 5VDC Closed Open Open Closed GND GND Pulse Transmission 1 gt 2 GND 5VDC GND Open Closed Closed Open t Pulse i i L d j Figure 4 Diagram and drive signal configuration for the E Tek fiber optic switch This can be done by observing the S and P channel outputs directly using a scope or by using the S Mean and P Mean indicators in the Scanning OFDR Software see Sec 3 1 2 Remove any strong reflectors from the test arm of the interferometer during this process
50. board The OFDR system hardware currently utilizes one of two data acquisition boards a PCI 6115 physically located within the HP workstation and accessed via the BNC 2110 connector block and a PXTe 4492 physically located in the PXIe 1073 chassis The PCI 6115 supports all of the above modes with a maximum clock rate of 10 MHz and 12 bit resolution The PXTe 4492 supports only the Sweep Int Clock and No Sweep SW trigger modes with a maximum clock rate of 204 8 MHz and 24 bit resolution 53 Called by Custom VIs called Labview VIs called DAQ Read vi Scanning OFDR 2 2 vi OFDR Global vi DAQmx Stop Task vi DAQmx Start Task vi DAQmx Read vi DAQmx Fill In Error Info vi Inputs 4 LV Class Name Description DAQmxName DAQmx Sweep Data acquisition task name If empty the task configured Capture Task by DAQ Config v3 vi is used if 1t exists Use Active Cluster Error In Input error cluster Boolean Start Task F Digital Timeout 30 sec Time to wait for data acquisition task to complete Outputs 2 LV Class Name Description Array Data Acquired data array Cluster Error Out Output error cluster VI description This VI reads data from a data acquisition task initiated by DAQ Config v3 vi 54 Called by Custom VIs called Labview VIs called DriveOpticalSwitch vi Scanning OFDR 2 2 vi None DAQmx Wait Until Done vi DAQmx Start Task vi DAQmx Create Virtual Channel vi DAQmx Create Channel CO Puls
51. ction shown in Fig 13 Scan Type Selects a 1D or 2D scan Axis 1 Settings Specifies the scan settings for a 1D scan or for the first axis of a 2D scan Axis 2 Settings Specifies the scan settings for for the second axis of a 2D scan Scan Initiates a scanned OFDR measurement Abort Aborts any scanned measurement currently in progress Each Axis Settings cluster contains the following fields Axis Selects the stage axis to move Steps Sets the number of steps to move Axis during the scan Direction The direction to move Axis during the scan Current Step Displays the current step for the axis during the scan Outside of these controls scanned measurements also make use of a few controls outside of the Scanning area The Axis settings refer to axes on the stack specified by Active Stack Each scan step moves Axis a distance set by the corresponding element in Step At each scan location the number of wavelength sweeps that are performed are set by Number of Sweeps 30 E f bA rd o a5 N A ES Peak Quantity Figure 14 The 2D Scan Plot display Displaying Scan Data The Scanning OFDR software provides two ways to display scan data a 2D intensity plot for visualizing 2D scan data and a line graph for plotting 1D scan data or slices through 2D scan data sets These plot options are accessed from the Supplemental Information Display selector Selecting 2D Scan Plot displays the intensity plot shown in Fig 14 This plo
52. cture of the tuning rate variations right The nominal wavelength tuning rate setting was 40 nm s single mode fiber a manual polarization controller PCO is included inline between the laser and the HP 8169A This manual polarization controller and the orientation of the polarizer in the HP 8169A should be adjusted to maximize the optical power output through the HP 81694 e The laser has three possible tuning rate settings for wavelength sweeps 0 5 nm s 5 nm s and 40 nm s The Scanning OFDR software always uses the 40 nm s setting because faster wavelength sweeps allow less environmental noise to couple into the measurement This tuning rate setting is a nominal value The actual tuning rate varies rapidly during a sweep See Fig 2 for plots of the measured tuning rate for a representative sweep The OFDR Fiber Optic Network e The network is constructed using Corning SMF28 fiber Use this or an equivalent fiber for any modifications e Fiber networks consists of three branches that are broken out by the fiber subsystem housed in the red Thorlabs box One branch is the main OFDR interferometer sec ond branch contain a H CN gas cell which is a NIST traceable wavelength reference over the range of 1525 1565 nm The third branch is a fiber Mach Zehnder interferom eter often called the trigger interferometer which provides a frequency clock signal for triggering data acquisition tasks e The gas cell is a dBm Optics model WA
53. culations begin by selecting a number of data points surrounding the specified peak locations This plot shows the se lected data points for each calculation This plot is useful for example for ensuring the set of points used for amplitude measurements is centered on the peak or to see whether or not the precision ranging filter window includes neighboring peaks which should be avoided The Plot selector provides the following choices Amplitude Measurements Precision Ranging and Precision Ranging Phase The first two options show the time domain data subsets used for the amplitude and precision ranging calculations respec tively The third option displays the frequency domain phase of the precision ranging data subset Within the plot window there will be one curve for each peak configured in the Peak Selection and Measurements array The visibility of each curve may be toggled using the checkbox next to the plot name in the plot legend Amplitude Chart Each time an amplitude measurement is performed the resulting values are added to this chart The horizontal axis is measurement number and the verti cal axis is amplitude measurement value There will be one curve for for each peak configured in the Peak Selection and Measurements array The visibility of each curve may be toggled using the checkbox next to the plot name in the plot legend Whether visible or not the data points stored in this chart are used to determine the amplitude mea
54. d Step Outputs 7 Name Acceleration Out Active Stack Out Canceled Drive Speed Out error out Startup Speed Out Step Out Description Stage axis acceleration settings array Stage stack selection Apply changes to stage values Close dialog and discard changes Stage axis drive speed settings array Input error cluster Close dialog and apply changes to stage values Stage axis startup speed settings array Stage axis step distance settings array Description Stage axis acceleration settings array Stage stack selection Indicate if the user canceled the operation Stage axis drive speed settings array Output error cluster Stage axis startup speed settings array Stage axis step distance settings array 112 VI description This VI provides a dialog user interface to modify Seruga Seiki stage settings 113 Sweep Agilent Laser 2 vi Called by Scanning OFDR 2 2 vi Custom VIs called OFDR Global vi Agilent Sweep Actions vi Agilent Laser On Off vi Labview VIs called None Inputs 1 LVClass Name Description Cluster Error In Input error cluster Outputs 1 LVClass Name Description Cluster Error Out Output error cluster VI description This VI initiates a wavelength sweep with the Agilent 81680A tunable laser 114 Called by Custom VIs called Sweep Mgr Q Cleanup vi Scanning OFDR 2 2 vi Communication States ctl Labview VIs called None Inputs 2 LVClass Name Desc
55. d using the stage motion pulse signal as the acquisition clock so that one data point is acquired on each analog input channel for each tick that the stage axis moves Smoothing Toggles application of a digital smoothing filter to confocal scan data Because the OFDR system is a coherent system confocal scan data often displays oscillatory character as a function of position due to interference effects These oscillations can make it difficult to locate confocal reflection peaks The oscillations can often be re moved in postprocessing through the application of a digital low pass filter The filter is a dual sided amplitude only filter with a flat passband and Gaussian roll off Smoothing Filter Cutoff The width of the flat passband of the smoothing filter in units of ticks Smoothing Filter Rolloff The 1 e width of the Gaussian rolloff of the smoothing filter in units of ticks Stage Software Limits Software limits may be applied to the Seruga Seiki stage axes so that axis motion does not go beyond user configured positions To configure the stage software limits select the menu option System Stage Limits This brings up the SS Stage Limits dialog window shown in Fig 10 The upper left portion of this dialog window houses the following controls Stack Selects the active stage stack 25 gt 43 Edit Stage Limits vi SS Stage Software Limits Current Position Stack Axis High Limit Low Limit Software Limits En
56. during pre cision ranging data processing Should be changed by selecting System Measurement Options Specifies the end wavelength for wavelength sweeps Specifies the end wavelength for wavelength sweeps Exit the Scaning OFDR software application 14 LVClass String Digital XYGraph Digital Digital Digital Array Enum Array Boolean Digital Boolean Digital Table 4 User interface control descriptions continued Name Filename Root Filter Size Pts Graph Main Laser Power mW P Mean Peak Area Pts Peak Array Plot Selection Position Recalculate S Mean ShiftLimits Start Wavelength Description Filename root for saving raw OFDR data during scanning The number of data points used for precision rang ing data processing Should be changed by selecting System Measurement Options Main plot area for displaying measurement results Specifies the laser output power Indicates the mean raw data value on the P channel During ordinary operation polarization controller PC1 should be adjusted so that S Mean and P Mean are equal The number of data points used for calculating peak amplitude values Should be changed by selecting System Measurement Options the Peak Selection and Measurements array this ar ray is used to specify peaks used for measurements and to display measurements associated with those peaks Specifies the quantity to be displayed in the m
57. e Startup Speed This is an array of six current startup speed values with one entry for each axis of the active stage stack The startup speed for an axis is the speed at which motion begins in units of ticks s Valid startup speed values are in the range 10 9999 Acceleration This is an array of six acceleration values with one entry for each axis of the active stage stack The acceleration setting for an axis is the rate at which motion accelerates beginning at Startup Speed and accelerating to Drive Speed in units of ticks s Valid acceleration values are in the range 0 9999 23 F 13 Stage Settings Dialog vi Seruga Seiki Stage Settings Active Stack Startup Speed Acceleration Drive Speed Step BEBE Cancel Apply Figure 8 The Seruga Seiki Stage Settings dialog window Drive Speed This is an array of six drive speed values with one entry for each axis of the active stage stack the drive speed for an axis is the speed in units of ticks s at which motion takes place following a period of acceleration Valid drive speed values are in the range 1 999 999 Step A duplicate of the Step array in the Seruga Seiki Stage Settings area of the main user interface Driving the Stages The title bar of the lower right region of the user interface is a drop down menu where one of the options is Motion Control Under this heading are the controls to remotely drive the Seruga Seiki stages This set of controls is shown in Fig
58. e Generation Time vi DAQmx Clear Task vi Inputs 2 LV Class Name Description Cluster error in Input error cluster Boolean State T close Requested fiber optic switch state Outputs 1 LV Class Name Description Cluster error out Output error cluster VI description This VI uses the counter outputs ctr0 and ctrl on the PCI 6115 data acquisition board to drive the E Tek fiber optic switch 55 Called by Custom VIs called Edit Hardware Parameters vi Labview VIs called None LVClass Boolean Array Enum Cluster Digital Boolean Digital Digital Digital LVClass Cluster Inputs 9 Name Cancel Channel Assignments amp Coupling DAQ Board error in no error Laser GPIB Address OK Stage GPIB Address Trigger Delay ns Trigger Hysteresis V Outputs 1 Name error out Scanning OFDR 2 2 vi OFDR Global vi Description Discard changes an close the dialog window Analog input channel configuration array Data acquisition board selection Input error cluster GPIB address of the Agilent 81680A tunable laser Apply changes and close the dialog window GPIB address of the Seruga Seiki D120 motion controller Trigger interferometer delay in nanoseconds Trigger hysteresis level in volts Description Output error cluster VI description This VI presents a dialog interface allowing the user to modify hardware parameters for the OFDR system
59. e A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Digital Distance Step distance value Allowable values are 0 8000000 Cluster error in Input error cluster Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Sets the step distance value for the specified Seruga Seiki stage axis 103 Called by SS Set Drive Speed vi Scanning OFDR 2 2 vi Stage Settings Dialog vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 3 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Digital Drive Speed Drive speed value Allowable values are 1 999999 Cluster error in Input error cluster Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Sets the drive speed value for the specified Seruga Seiki stage axis 104 SS Set Position Value vi Called by Set Postion Label vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 3 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Digital Position Value Position value Allowable values are 1 999999 Outputs 1 LV Class Name Description Cluster error out Output error cluster VI description Sets the position value for the specified Seruga Seiki stage axis Note that this VI do
60. e Description Array Data Set Sizes The number of data points in the data sets corresponding the returned sweep ranges Array Sweep Ranges The wavelength sweep ranges corresponding to data set sizes equal to powers of 2 VI description This VI determines the wavelength sweep ranges corresponding to data set sizes that are equal to powers of 2 The largest data set size is always 2 anda number of ranges specified by of Ranges is returned 119 Called by Custom VIs called Labview VIs called WL vs Time vi Scanning OFDR 2 2 vi OFDR Global vi Fourier Interpolation vi NI_AALPro Ivlib Unwrap Phase vi NILAALPro Ivlib Fast Hilbert Transform vi NI_AALBase lvlib Mean vi Inputs 5 LV Class Name Digital Clock rate Hz Digital Interferometer Delay ns Digital Interp Factor Array Raw Data Digital Start WL nm Outputs 4 LVClass Array Digital WaveformGraph Array Name Frequency GHz Time step ms Waveform Graph Wavlength nm Description Data acquisition sampling rate Relative delay between the interferometer paths Factor by which to Fourier interpolate the Raw Data prior to the Hilbert transform Time sampled wavelength sweep data for a simple path mismatched interferometer Sweep start wavelength Description Measured frequency vs time data Time step size for wavelength and frequency output data arrays Measured wavelength vs time data VI description Th
61. e amplitude of the reflector as well as the position of the reflector To perform these analyses peaks must be specified by the user so that the software is able to locate the desired peaks within the OFDR time domain data set Peak specification is ac complished using the Peak Selection and Measurements array shown in Fig 7 Each element of the Peak Selection and Measurements array is a cluster of controls that may be associated with a single reflection peak The elements of each Peak Selection and Measurements cluster are Peak The peak number used to refer to the peak This value is always equal to the element number within the array 20 Location The location of the peak within the OFDR time domain data set in nanoseconds Cursor List A list of the available cursors in the Main Graph When cursors are added removed or changed in the Main Graph the Cursor List must be manually updated by clicking Refresh Cursor List Colorbox The color of the cursor currently selected in Cursor List Pickup Sets Location to the time axis value of the Main Graph cursor currently selected in Cursor List Lock Locks Location to the time axis value of the Main Graph cursor currently selected in Cursor List When Lock is on Location will automatically update when the position of the selected cursor is changed Amplitude Indicates the measured amplitude of the peak Amplitude Mean Indicates the mean of recent amplitude measurements of the peak The
62. e manual knobs on the stages may be turned Motor power is indicated on the D120 motion controller by the case of the axis label Uppercase ex A1 indicates axis power is on while lowercase ex al indicates axis power is off 110 Called by SS Toggle Software Limits vi Edit Stage Limits vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 3 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Boolean Enable Software limit setting True On False Off Cluster error in Input error cluster Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Toggles software limits on and off for the specified Seruga Seiki stage axis 111 Called by Custom VIs called Labview VIs called LVClass Array Enum Boolean Boolean Array Cluster Boolean Array Array LVClass Array Enum Boolean Array Cluster Array Array Stage Settings Dialog vi Scanning OFDR 2 2 vi Stage Setting Array ctl SS Set Start Up Speed vi SS Set Remote Mode vi SS Set Drive Speed vi SS Set Distance vi SS Set Acceleration vi SS Query Start Up Speed vi SS Query Drive Speed vi SS Query Distance vi SS Query Acceleration vi OFDR Global vi Active Stack Enum ctl None Inputs 9 Name Acceleration Active Stack Apply Cancel Drive Speed error in no error OK Startup Spee
63. elevant differences between the two DAQ boards e Both DAQ boards receive a start trigger signal from the laser the Trigger Out connector on the back of the Agilent 81680A The current hardware configuration has this trigger signal wired to pin PFI6 on the PCI 6115 DAQ board though it can be wired to any available PFI pin The PXIe 4492 must receive the start trigger signal on pin PFIO because it is the only pin on the board other than the analog input channels The name of pin where the start trigger signal is applied is stored in the Scanning PFIO on the PCI 6115 is the external analog clock pin so it is not available for the start trigger signal 11 2 4 2 5 OFDR software under the global variable Start Trig Pin The Seruga Seiki Stage System The minimum incremental linear motion for the Seruga Seiki stages is approximately 40 nm This unit is referred to as one tick The settings and positions of the linear stages are all communicated through the Seruga Seiki D120 motion controller in units of ticks The minimum incremental rotational motion for the Seruga Seiki stages is approxi mately 1 6 millidegrees This unit is also referred to as a tick in the context of rotational motion Communication with the Seruga Seiki D120 motion controller takes place via GPIB but the D120 does not respond to the standard IDN query See the D120 Series Stepping Motor Controller Instruction Manual for a complete listing of acc
64. ename incorporating the registered user name and a timestamp is provided The file is saved with a ini extension The contents of the file is ascii text with 33 r 13 Save Options Dialog vi Configure Autosave Options Autosave Raw Data Autosave Data Folder g Filename Root Cancel Figure 17 The Configure Autosave Options dialog window a key value format for each parameter While configuration files are human readable and editable outside of the Scanning OFDR software application manual editing is not recommended to avoid invalid keys and values Once a configuration file has been saved the Scanning OFDR software application may be restored to the saved state by selecting the menu option File gt Load Configuration File to load the configuration file 3 2 SubVI Listing The following is a listing of all custom subVIs called by the Scanning OFDR software applica tion Scanning OFDR v2 2 vi These VIs also make use of VIs supplied by National Instruments with the LabVIEW 2011 installation as well as VIs available through the OpenG project See OpenG org for more information on OpenG VIs 34 Agilent Cycle Number vi Called by Agilent Startup Sequence vi Custom VIs called None Labview VIs called None Inputs 3 LVClass Name Description Cluster error in Input error cluster Digital GPIB Address GPIB address of the Agilent 81680A tunable laser Digital Number of Sweep Requested number of sweeps Allow
65. epted GPIB commands For confocal scanning with the Scanning OFDR data is acquired as a function of stage position This is accomplished using either the CW pulse signal or the CCW pulse signal as an external clock for triggering data acquisition during motion These signals are accessed from the Monitor Output on the back of the D120 controller The connector for the Monitor Output is apparently obsolete and the closest Digi Key part number is not compatible As a result there is a custom connector made from a modified DX40M 20P connector that interfaces to the Monitor Output This connection isn t as secure as it should be so exercise care to make sure the connection is maintained When the D120 applies power to the stage axes the knobs on the stage stack become locked Axis power must be turned off before the knobs can be turned It is best to avoid turning the knobs and instead drive the stages using the Scanning OFDR software see Stage Software Limits in Sec 3 1 5 Alternatively use the Handy Terminal connected to the D120 controller to drive the stages See the D120 Series Stepping Motor Controller Instruction Manual for instructions on how to use the Handy Terminal and for further information about the Seruga Seiki stages The Control Computer This computer is currently an HP xw4600 workstation with an Intel Core2 Duo E8400 3 00 GHz CPU and 6 0 GB of RAM Presumably this computer will be replaced with an upgr
66. es not move the stage but only changes the position label value for the current position 105 SS Set Remote Mode vi Called by Scanning OFDR 2 2 vi Stage Settings Dialog vi Edit Stage Limits vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 1 LVClass Name Description Cluster error in Input error cluster Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Sets the Seruga Seiki D120 motion controller to remote mode This VI must be called before calling any other SS Stage VIs 106 SS Set Software Limit vi Called by Set Postion Label vi Edit Stage Limits vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 4 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Boolean Hi Limit Specifies whether to set the clockwise limit True or the counterclockwise limit False Digital Position Value The requested position of the software limit Outputs 2 LV Class Name Description Cluster error out Output error cluster Digital Limit Value Out The actual value of the specified software limit VI description Sets the position of the software limits for the specified Seruga Seiki stage axis 107 SS Set Start Up Speed vi Called by Scanning OFDR 2 2 vi Stage Settings Dialog vi Custom VIs called OFDR Global vi Labview
67. escription This VI processes raw wavelength sweep data to produce the OFDR data plotted in the main graph of the Scanning OFDR software application Process ing includes the optional application of a window function Fourier transform and combina tion of the S and P channel data 72 Called by Custom VIs called Labview VIs called Peak Amplitudes2 vi Scanning OFDR 2 2 vi Peak Cluster3 ctl NI_AALBase Ivlib Std Deviation and Variance vi Inputs 7 LVClass Name Description LVObjectRefNum Chart_AM A reference to the Amplitude chart on the front panel of the main Scanning OFDR software application Array Data OFDR plot data Digital Data Buffer Size The number of OFDR data points Cluster error in no Input error cluster error Digital Peak Area Pts The number of points to integrate in the peak amplitude calculation Array Peak Array The Peak Selection and Measurements array passed from the main Scanning OFDR VI Digital TrigDelay Reciprocal of the frequency spacing of the OFDR data set Outputs 3 LVClass Name Description Cluster error out Output error cluster Array Peak Array Out Output Peak Selection and Measurements with updated amplitude measurement values Array Peak selections The data points used for each peak amplitude calculation VI description This VI calculates reflection peak amplitudes from OFDR mea surement data for reflection peaks specified by the user in the Peak Selection and Measure men
68. ested specificed by Plot Selection and the parameters describing the data acqusition specified by Acquisition Parameters 62 Get Channel Assignments vi Called by Scanning OFDR 2 2 vi Precision Ranging2 vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 1 LVClass Name Description Cluster error in no Input error cluster error Outputs 5 LVClass Name Description Digital Aux Aux channel assignment Cluster error out Output error cluster Digital HCN HCN channel assignment Digital P P channel assignment Digital S S channel assignment VI description Data manipulation functions generally expect data acquired on a specific channel Within the OFDR software these channels are specified by name and the user may associate each name with any available physical analog input channel This VI returns the analog input channel number associated with the S P Aux and HCN channel names 63 Handle Peak Array vi Called by Scanning OFDR 2 2 vi Custom VIs called Peak Cluster3 ctl Labview VIs called None Inputs 6 LVClass Name Array Chart Refs Cluster error in no error LVObjectRefNum Main Graph Ref Array Peaks New Array Peaks 01d Array WFGraphs Outputs 5 LVClass Name Cluster error out Array Peaks Out Boolean Recalc Amp Boolean Recalc PR Boolean SameSize Description Input error cluster Reference to the Main Graph on the front panel of the main Scanning OFDR program
69. figured in the Peak Selection and Measurements array in the main Scanning OFDR program For each peak the user may select the save amplitude or precision ranging data or both For each peak the user may also enter a prefix used for the data filenames Amplitude data files will have Amp appended to the prefix and range data files will have Range appended to the prefix A timestamp may also optionally be appended to the filenames Data are saved in a tab delimited ASCII spreadsheet format 86 Scan Manager vi Called by Custom VIs called Scanning OFDR 2 2 vi Stage Parameter ctl Scan Type Enum ctl Scan Axis Settings ctl Communication States ctl Axis Selector ctl Labview VIs called None Inputs 7 LVClass Name Digital Sweeps Boolean Abort Scan Cluster Axis 1 Settings Cluster Axis 2 Settings Cluster error in no error Enum Scan Type LVObjectRefNum Step Ref Outputs 4 LVClass Name Cluster Axis 1 out Cluster Axis 2 out Cluster error out Array Queue States Description The number of wavelength sweeps to perform at each scan location Aborts current scan Specifies the scan settings for a 1D scan or for the first axis of a 2D scan Specifies the scan settings for the second axis of a 2D scan Input error cluster Selects a 1D or 2D scan Reference to stage axis step distance settings array on the main OFDR front panel Description Scan settings cluster output with updated Current
70. for data acquisition A rule of thumb is that the hysteresis level should be about one quarter to one half of the amplitude of the analog clock signal See Level Triggering with Hysteresis on page 13 5 of the National Instruments DAQ S Series User Manual for mor information Channel Assignment This lists the available analog input channels for the selected DAQ Board 17 Signal Name Assigns device independent signal names to the various analog input channels Data processing functions in the Scanning OFDR software look for signals named S P HCN and Aux Signal names must be unique for each analog input channel Input Coupling Selects AC or DC coupling for each analog input channel In general all channels should be DC coupled The S and P channels may be AC coupled to increase the signal to noise ratio for small amplitude reflectors but this approach must be used with caution especially with regard to balancing the polarization diverse detection channels High Limit V Set the highest expected voltage to be measured on each analog input channel Note this level is used to select an available gain setting on the selected DAQ Board and is not a firm fixed limit Low Limit V Set the lowest expected voltage to be measured on each analog input chan nel Note this level is used to select an available gain setting on the selected DAQ Board and is not a firm fixed limit Once all parameters have been set click OK to accept the change
71. g window Autosaving Raw Data The Scanning OFDR software provides an option to automatically save raw data each time a new acquisition is performed Caution autosaving raw data can produce extremely large amounts of data Before enabling autosaving for extensive measure ment processes such as scanned OFDR measurements make sure sufficient hard disk space exists to store all of the data To configure autosaving of raw data select File Configure Autosave This brings up the Configure Autosave Options dialog window shown in Fig 17 This window provides the following controls Autosave Raw Data Enable or disable autosaving using this checkbox Autosave Data Folder The hard disk location where autosaved data is stored Filename Root A string prefix used for filenames Filenames also include a timestamp Loading Raw Data Raw data files with a ofdr extension may be loaded back into the Scanning OFDR software application for viewing or further data processing To load a raw data file select File gt Load Raw Data 3 1 10 Saving and Loading System Configuration The current state of the Scanning OFDR software application including the values of front panel controls and hardware parameters but excluding data currently in memory may be saved to a configuration file by selecting the menu option File gt Save Configuration File A dialog window will appear with a prompt to select the filename and folder location to save the file and a default fil
72. i This software application provides all user interface hardware control and data processing functions to perform a variety of measurement tasks A screen capture of the main user interface is shown in Fig 5 A listing of the controls found on the front panel of the user interface appears in Table 4 Table 4 Alphabetical list of user interface controls for the Scanning OFDR software with descriptions LVClass Name Description Digital Sweeps Specifies the number of wavelength sweeps to be per formed when the Sweep button is pressed or at each location of a scan Enum Active Axis Specifies the currently active Seruga Seiki stage axis Enum Active Stack Specifies the currently active Seruga Seiki stage stack 13 LVClass Boolean Digital Boolean Enum Digital Enum Boolean Digital Array Digital Digital Ring Boolean Table 4 User interface control descriptions continued Name Autosave Raw Data Aux Mean Averaging Averaging Domain Clock Freq Hz Clock Source Continuous Data Buffer Size Drive Speed Endpoints EndWLnum EndWLring EXIT Description Toggle saving of raw OFDR data during scanning When turned on a dialog window prompts the user to specify a data directory and file name prefix for saved data Cau tion saving raw data can produce extremely large amounts of data Be aware of available disk space and save a single raw data file before beginning to determine
73. is VI calculates the laser wavelength versus time from time sampled wavelength sweep data for a simple interferometer on the Aux channel with a relative delay equal given by Interferometer Delay ns This VI uses the Hilbert transform method described in Ahn et al Applied Optics 44 35 7630 The sampling density of the raw data is optionally increased by a factor of Interp Factor prior to the Hilbert transform by Fourier interpolation using zero padding 120
74. lay this VI determines the sweep end wavelength for a radix 2 data set nearest to the previous sweep end wavelength setting It also provides a set of six wavelength ranges corresponding to data set sizes of 2 raised to the powers of 14 through 19 These ranges are not always appropriate especially for short trigger interferometer delays so this VI should be updated with a more robust range selection algorithm 116 Update Scan Data vi Called by Scanning OFDR 2 2 vi Custom VIs called None Labview VIs called NI_AALBase Ivlib Mean vi Inputs 6 LVClass Name Digital Sweeps Array Chart Refs Digital Current Step 1 Digital Current Step 2 Cluster error in no error Array Scan Data Outputs 2 LVClass Name Cluster error out Array Updated Scan Data Description The number of wavelength sweeps to average at each scan location References the Amplitude Chart and Range Chart on the front panel of the main Scanning OFDR software appli cation organized in an array Current scan step along Axis 1 Current scan step along Axis 2 Input error cluster Scan data array see VI description Description Output error cluster Updated scan data array VI description This VI updates the Scan Data array each time an OFDR mea surement has completed during a scanned measurement The Scan Data array contains amplitude and range data at each scan position for each peak configured in the Peak Se lection and Measurements
75. lled None Labview VIs called None Inputs 15 70 LVClass Name Array Axis Labels Digital c m s Array Channel Assignments amp Coupling Enum DAQ Board Digital Ext clock level V Digital Hysteresis V Digital Laser GPIB Address Digital Stage Angular Tick deg tick DAQmxName Stage CCW Pulse Pin DAQmxName Stage CW Pulse Pin Digital Stage GPIB Address Digital Stage Linear Tick nm tick DAQmxName Start Trig Pin Ring Sweep Rate nm s Digital TrigDelay Outputs 1 LV Class Name DAQmxName DAQmx Sweep Capture Task VI description Description OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig OFDRConfig Description OFDRConfig 71 OFDR Plot Data vi Called by Scanning OFDR 2 2 vi Custom VIs called OFDR Global vi Labview VIs called NI_AALPro lvlib Real FFT vi NIL AALPro Ivlib Hanning Window vi NI_AALPro vlib Hanning Window DBL vi NI_AALPro Ivlib Flat Top Window vi NI AALPro Ivlib Flat Top Window DBL vi NI_AALPro vlib FFT vi Inputs 3 LVClass Name Description Cluster error in no Input error cluster error Array Raw Data Raw wavelength sweep data array Enum Window Window function applied to the raw data prior to the Fourier transform Outputs 2 LVClass Name Description Cluster error out Output error cluster Array OFDR Data Processed OFDR data VI d
76. lockwise limit False Outputs 2 LVClass Name Description Cluster error out Output error cluster Digital Limit Value Out The position of the requested software limit VI description Queries the position of the software limits for the specified Seruga Seiki stage axis 98 SS Query Start Up Speed vi Called by Scanning OFDR 2 2 vi Stage Settings Dialog vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 2 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Outputs 2 LV Class Name Description Cluster error out Output error cluster Digital Startup Speed Current startup speed setting VI description Queries the start up speed setting for the specified Seruga Seiki stage axis 99 SS Query Status vi Called by SS Monitor vi Edit Stage Limits vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 2 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Outputs 2 LV Class Name Description Cluster error out Output error cluster Cluster Status Cluster Axis status cluster VI description Queries the status of the specified Seruga Seiki stage axis The Status Cluster output by this VI includes the following boolean indicators format Axis
77. ls in Scanning OFDR 2 2 vi via control references Data is a two element boolean array cast as a variant in order to be passed by queue in the calling VI If the first element in the boolean array is true the axis moves to position zero If the first element is false the axis move it s current step distance The second element of the boolean array indicates direction True for clockwise False for counterclockwise Motion may be aborted within the calling VI via the Stop ref boolean control reference 69 OFDR Global vi Called by Scanning OFDR 2 2 vi Agilent Query Sweep State vi Sweep Agilent Laser 2 vi Agilent Startup Sequence vi DAQ Read vi DAQ Config v3 vi Set Postion Label vi SS Set Software Limit vi SS Query Software Limit vi SS Query Position vi SS Set Position Value vi Move SS Stage vi SS Stop vi SS Query Status vi SS Go To Position vi SS Drive Axis vi SS Select Axis vi SS Query Distance vi SS Query Acceleration vi SS Query Start Up Speed vi SS Query Drive Speed vi SS Toggle Motor Power vi SS Set Remote Mode vi SS Set Acceleration vi SS Set Distance vi SS Set Drive Speed vi SS Set Start Up Speed vi Check Instruments vi Resample vi WL vs Time vi Get Channel Assignments vi Calculate Tilt vi Confocal Plot Data vi OFDR Plot Data vi Generate X Axis vi Signal Levels vi Buffer Points vi Edit Hardware Parameters vi Stage Settings Dialog vi Edit Stage Limits vi SS Toggle Software Limits vi Custom VIs ca
78. motion was interrupted Indicate if axis is moving Stage axis position array VI description This VI is intended to be called in a loop to monitor a Seruga Seiki stage axis during motion It reports the position and status of the axis and allows motion to be interrupted 93 SS Query Acceleration vi Called by Scanning OFDR 2 2 vi Stage Settings Dialog vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 2 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Outputs 2 LV Class Name Description Digital Acceleration Current acceleration setting Cluster error out Output error cluster VI description Queries the acceleration setting for the specified Seruga Seiki stage axis 94 SS Query Distance vi Called by Scanning OFDR 2 2 vi Stage Settings Dialog vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 2 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Cluster error in Input error cluster Outputs 2 LV Class Name Description Digital Distance Current step distance Cluster error out Outpur error cluster VI description Queries the step distance for the specified Seruga Seiki stage axis 95 SS Query Drive Speed vi Called by Scanning OFDR 2 2 vi Stage Settings
79. n and standard deviation values reported in the Peak Selection and Measurements array for each peak Remove all stored data by clicking Clear Chart Range Chart Each time a precision ranging measurement is performed the resulting values are added to this chart The horizontal axis is measurement number and the vertical axis is range in picoseconds There will be one curve for for each peak configured in the Peak Selection and Measurements array Toggle visibility of each curve as in the Amplitude Chart using the checkbox next to the plot name in the plot legend Whether visible or not the data points stored in this chart are used to determine the range mean and standard deviation values reported in the Peak Selection and Measurements array for each peak Remove all stored data by clicking Clear Chart 22 The Use Cursor Colors checkbox is present when any of these three options is selected It provides an easy way to color code peaks among the Main Graph the Peak Selection and Measurements array and supplemental graphs and charts by setting the supplemental plot colors to match the associated Colorbox value in the Peak Selection and Measurements array which in turn matches the color of a cursor in the Main Graph which may be used to specify the peak location Turning Use Cursor Colors off allows the user to freely set the plot colors in graphs and charts 3 1 5 Motion Control The Scanning OFDR software provides direct control over the Seruga
80. ned transversely This requires that the planar interface of the sample must be oriented so that it is parallel to the transverse stage axes and perpendicular to the axial stage axis This process assumes the optical axis of the probe beam has been previously aligned to the axial stage axis The Scanning OFDR software provides an automated sample perpendicularization process This process consists of the following steps 1 Move transversely a known step size along one transverse axis 2 Measure the axial location of the reflecting interface 3 Move transversely a known step size in the opposite direction along the same transverse axis 4 Measure the axial location of the reflecting interface again 5 Calculate the tilt angle of the interface as the inverse tangent of the difference in axial locations of the interface over the difference in transverse measurement positions 28 Perpendicularization Method Transverse Axis Confocal Axis Peak Transverse Step Tilt Angle Measure Tilt Adjust Angle Figure 12 The Perpendicularization control group 6 Rotate the sample an amount equal to the measured tilt angle 7 Repeat this process for the other transverse axis To set parameter values and initiate the perpendicularization routine use the following con trols found under the Perpendicularization heading selection shown in Fig 12 Method Selects the method used for determining the axial position of the reflector
81. nformation on using the Handy Terminal If it is necessary to perform manual stage motion by turning the knobs on the stage axes axis power must first be turned off through the Scanning OFDR software interface This is accomplished by selecting the menu option System Allow Manual Motion When this menu option is checked stage axis power is turned off and the axis knobs are unlocked The Drive Axis controls also become disabled This option should remain unchecked during normal operation which keeps power applied to the stage axes and locks the axis knobs 3 1 6 Peak Optimization When using a focused probe beam to perform reflectivity measurements using the Scanning OFDR it is important to position the sample interface of interest precisely at the focus of the probe beam This is because reflected light must couple back into a single mode fiber core which acts as a confocal filter and rejects reflections from outside the focal region This means that the measured amplitude of reflection peaks will exhibit a maximum when the interface is positioned at the focus and fall off as the interface moves axially in either direction For reflection peaks positioned near the focus the Scanning OFDR software can automatically optimize the measured reflection amplitude by moving the sample axially and monitoring the peak amplitude as a function of position This process is referred to as Peak Optimization and is accomplished using the controls under the Pe
82. nt control Controls inside tabs are parsed before getting passed to Read Key Variant vi so they are not subject to this limitation Configuration file keys must match control labels 65 Load OFDR Config vi Called by Custom VIs called Labview VIs called Data vi OpenG VIs called Inputs 5 LVClass Name Path configuration file path LVObjectRefNum Cursor Cluster error in no error LVObjectRefNum Graph Main Ref VIRefNum VI reference Outputs 2 LV Class Name Cluster error out VIRefNum VI reference out Scanning OFDR 2 2 vi Load Configuration vi NI_LVConfig Ivlib Open Config Data vi NI_LVConfig Ivlib Close Config Read Key Variant __ogtk vi Description The path to the platform independent configuration file Reference to the Cursor enum in the Peak Selection and Measurements array on the front panel of the main OFDR program interface Input error cluster Reference to the main graph on the front panel of the main OFDR program interface Reference to the VI being configured Description Output error cluster Reference to the VI being configured VI description This VI loads control values for the main OFDR program in terface and OFDR Global vi from a configuration ini file Explicit references to the Main Graph and Cursor list are passed because properties of these controls other than their values are loaded from the configuration file 66 Called by Custom VIs called
83. of endpoints to neglect during precision ranging linear curve fit Number of points used for the precision ranging digital filter Number of points used for peak amplitude calculation VI description This VI presents a dialog interface for the user to modify options associated with peak amplitude and precision ranging measurements 68 Move SS Stage vi Called by Scanning OFDR 2 2 vi Custom VIs called SS Monitor vi SS Go To Position vi SS Drive Axis vi OFDR Global vi Log Manager vi Axis Selector ctl Active Stack Enum ctl Labview VIs called None Inputs 8 LVClass Name Enum Active Axis Enum Active Stack LV Variant Data Cluster error in Boolean Log LVObjectRefNum Position Ref LVObjectRefNum Status LVObjectRefNum Stop ref Outputs 3 LVClass Name Boolean At Limit Boolean Axis powered Cluster error out Description Stage axis selection Stage stack selection Queue data message See VI description Input error cluster Indicate whether to make an entry in the OFDR status log Reference to stage axis position array on the main OFDR front panel Reference to status log string control Reference to Stop control on the main OFDR front panel Description Indicates whether selected axis is at a limit Indicates whether selected axis is powered Output error cluster VI description This VI provides motion control of the Seruga Seiki stages It communicates with front panel contro
84. oftware limit settings to preserve 26 the same physical location upon a change in the zero location for a stage axis To enable this option select the menu option System gt Shift Limits With Zero When this option is checked limit settings are changed when the zero location for an axis changes preserving the same physical location for the limit When unchecked the software limit settings remain unchanged so a change in zero location for a stage axis results in a change in the physical location of the software limit Manual Stage Motion Best practice when using the Scanning OFDR system is to use the software interface to drive the stages and avoid manual stage motion by physically turning the knobs on the stage stacks This is because the Seruga Seiki D120 motion controller does not register manual motion and does not update the axis position in response to manual motion This results in a shift of the axis coordinate system by an unknown amount each time an axis knob is turned Because software limits are specified in the axis coordinate system manual motion causes a change in the physical location of the software limits potentially leading to damage if the stage overruns an intended limit location causing a collision An alternative means of manual stage motion that does not cause a change in axis coor dinate system is to use the Handy Terminal connected to the D120 motion controller See the Seruga Seiki D120 user manual for more i
85. on tag Only tagged controls are saved VIRefNum VI reference Reference to the VI whose configuration is being saved Outputs 3 LV Class Name Description Cluster error out Output error cluster TypedRefNum INI refnum out Configuration file reference VIRefNum VI reference out Reference to the VI whose configuration is being saved VI description This VI calls the OpenG function Write Key Variant to write front panel control values of the VI specied by VI Path to a configuration file specified by INI Path only if the beginning of the control description matches Tag Write Key Variant is recursive so that nested controls are handled Only tags for top level controls are checked however so for controls inside clusters or arrays all controls in the array are either written or not depending on the description tag of the parent control Controls inside tabs are parsed before getting passed to Write Key Variant so they are not subject to this limitation 83 Save OFDR Config vi Called by Scanning OFDR 2 2 vi Custom VIs called Save Configuration vi Labview VIs called NI_LVConfig Ivlib Open Config Data vi NI_LVConfig Ivlib Close Config Data vi OpenG VIs called Write Key Variant __ogtk vi Inputs 4 LVClass Name Description Path configuration The path to the platform independent configuration file file path Cluster error in no Input error cluster error LVObjectRefNum GraphMain Ref Reference to the main graph
86. ong reflector in the test arm remove it or pinch off the fiber if you know how to do this without breaking it when balancing the S and P signals 19 Peak Selection and Measurements Amplitude Mean Std Dev Ref Peak Range ps Mean Std Dev Peak Pickup Location Peak Pickup Location Pickup Pickup Figure 7 The Peak Selection and Measurements array OFDR Time Domain This options combines applies a window function specified by Win dow to the data acquired on the S and P channels prior to discrete Fourier transfor mation The two signal are then combined in quadrature to produce the data shown in the main graph Confocal This option display confocal scan data It is not available for wavelength sweep data and is grayed out when wavelength sweep data is in memory Group Delay This option is not yet implemented Windows Applying a window function to the raw data before Fourier transformation can aid in visualizing and interpreting OFDR data When no window is applied spectral leakage can cause broad shoulders on reflection peaks Application of a Hanning window reduces the effects of spectral leakage and can aid in resolving small reflection peaks A flat top window improves the scan to scan stability of peak amplitude measurements at the expense of resolution 3 1 4 Peak Selection and Measurements Once an OFDR measurement has been performed reflection peaks may be analyzed to pre cisely determine th
87. pecifies the current step sizes for each axis of the Seruga Seiki stage stack specified by Active Stack Units are ticks where 1 tick is approximately equal to 40 nm Supplemental Plots Tab Allows the user to display the various supplemental plots or the Status Log Add addi tional pages to this tab control for custom data process ing Initiates a laser wavelength sweep and data acquisition Sweep buffer for HCN wavelength calibration not yet im plemented Click to update the cursor lists in the Peak Selection and Measurements array to match the cursor legend for the main graph Indicates whether or not to contrain data set sizes to be a power of two This control is disabled toggle this fea ture using the menu option System Use 2 n Point Scan Range Displays the user logged in to the system To change the user select File gt Change User Specifies the window function to be applied to raw fre quency domain data prior to applying the Fourier trans form when calculating OFDR time domain data Upon starting the Scanning OFDR system software a dialog box will request registration of your user name Users who have registered with the system previously will find their names in the drop down list If your name is not in the list type your name and click OK Before performing measurements make sure that the current hardware state is accurately represented in the software settings To edit hardware parameters select
88. ription Cluster Error in Input error cluster TypedRefNum Queue In Queue reference Outputs 2 LVClass Name Description Cluster Error out Output error cluster TypedRefNum Queue Out Queue reference VI description When continuous wavelength sweeping is halted by the user or when a fixed number of sweeps is requested and sweeping is aborted before all sweeps have completed states may be present in the Communication Queue that should not execute This VI removes such states from the queue 115 Called by Custom VIs called Labview VIs called Update End WL vi Scanning OFDR 2 2 vi Wavelength Range vi LVStringsAndValuesArray TypeDef ctl Inputs 4 LVClass Name Description Digital End Wavelength Modified sweep end wavelength setting so that data set size is radix 2 Cluster error in no Input error cluster error Digital Start Wavelength Sweep start wavelength Digital Trigger Delay Trigger interferometer delay ns Outputs 3 LVClass Name Description Digital End Wavelength Current sweep end wavelength setting Array End WL Strings Cluster of strings and values representing wavelength And Values sweep ranges for six radix 2 data set sizes Cluster error out Output error cluster VI description The main Scanning OFDR software application allows the user to toggle between restricting data set sizes to be a power of 2 or allowing arbitrary data set sizes Given a sweep start wavelength and the trigger interferometer de
89. s and close the dialog window or click Cancel to discard all changes Note if the PXIe 4492 DAQ board is selected there are eight analog input channels but only four are displayed at a time Use the scroll bar to display the rest 3 1 2 Performing Swept Wavelength Measurements A swept wavelength measurement consists of sweeping the wavelength of the Agilent 81680A laser source digitizing and acquiring the output signals from OFDR system fiber optic net work and optionally performing data processing tasks on the resulting data The controls for performing basic swept wavelength measurements are located in the upper left corner of the user interface in the area labeled Swept Wavelength Acquisition To perform a basic swept wavelength measurement use the following procedure 1 Set the Start Wavelength and End Wavelength for the sweep The available wave length range for the Agilent 81680A tunable laser is 1460 to 1580 nm 2 Set the Laser Power Typical values for the laser power are 3 to 4 mW Note that when changing the laser power be sure to ensure that the resulting raw data does not saturate any of the analog input channels are the DAQ board Changing the laser power may also require a change in the Trigger Hysteresis 3 Choose a Clock Source Choices are External or Internal Internal uses the clock internal to the DAQ board External uses the external clock signal supplied by the Trigger Interferometer on PFIO of the PCI 6115 DAQ bo
90. t has the following options Peak Selects a peak from the Peak Selection and Measurements array for which to plot scan data Quantity Selects Amplitude or Range data to plot Selecting Scan Slice Plot from the Supplemental Information Display selector displays the graph shown in Fig 15 This graph has the same options for selecting Peak and Quantity as the 2D Scan Plot Additionally the following options are available Slice Direction When plotting a slice through a 2D scan data set this selects whether to use a slice parallel to Axis 1 or Axis 2 Slice Position Selects the array index of the slice within the 2D scan data set along the other axis which is not selected as the Slice Direction 3 1 9 Saving Data The Scanning OFDR software provides three options for saving data These options are found under the File menu 31 5159 5158 75 5158 5 5158 25 5158 5157 75 5157 5 5157 25 5157 5156 75 5156 5 5156 25 ee 0 2 3 4 Frequency THz Peak Plot 0 Phase rad Quantity Plot 1 Plot 2 Plot 3 Slice Direction Slice Position Figure 15 The Scan Slice Plot display Save Raw Data This option saves the raw data acquired directly from the analog inputs on the DAQ board without any additional data processing It also includes as header that records parameters describing the acquisition so that all data processing features of the Scanning OFDR software may be reproduced The data is stored as a binary file wi
91. tage Parameter ctl Log Manager vi Communication States ctl Axis Selector ctl Labview VIs called None Inputs 4 LVClass Name Cluster error in no error LVObjectRefNum Status Ref LVObjectRefNum Step Ref Cluster Tilt cluster Outputs 2 LVClass Name Cluster error out Array State array Description Input error cluster Reference to status log string control Reference to a stage axis step distance settings array in the calling VI Cluster of tilt measurement parameters see VI descrip tion Description Output error cluster Array of queue states to perform a tilt measurement VI description This VI enqueues the states necessary to perform a measurement of the tilt angle of a sample under test The steps in this process are as follows format 1 Set active axis to Transverse Axis 2 Set Transverse Axis step size to Transverse Step 3 Move CW 4 Measure distance 5 Move CCW twice 6 Measure distance 7 Move CW 8 Set Transverse Axis step size back to prior value Tilt measurement parameters are passed to this VI via the Tilt Cluster though not all elements of the Tilt Cluster are used The following elements are used format Transverse Axis Stage axis for transverse motion Transvese Step Transverse distance to move Method Tilt measurement method Currently only the Precision Ranging method is fully implemented Confocal Axis Confocal scan axis when using the Confocal method 60 Called by Cus
92. ted if Plot Selection is set to OFDR Time Domain This is because the precision ranging calculation uses the raw measurement data as a starting point while the amplitude calculation uses the OFDR time domain data including application of the window function specified by Win dow This data is only produced when Plot Selection is set to OFDR Time Domain If 21 wavelength sweep data is acquired with Clock Source set to Internal then range data is not updated since the precision ranging calculation relies on data sampled at equal increments of optical frequency The amplitude measurement does not have this requirement however so amplitude measurement values will update for new internally clocked data If the Peak Selection and Measurements array has been modified since the last wavelength sweep the measurement values may be updated without acquiring new data by clicking the Recalculate button Measurement Charts and the Selected Peaks graph Additional information about the peaks specified in the Peak Selection and Measurements array and the associated peak measurements can be found in the upper right of the main user interface in the Supplemen tal Information Display area Three of the options found in the Supplemental Information Display selector are relevant to peak selection and measurements The other options are described elsewhere in this document The options relevant here are Selected Peaks Both the amplitude and precision ranging cal
93. th a ofdr extension Save Main Graph Data This option saves the data present in the Main Graph of the Scanning OFDR user interface as a tab delimited text file The first column is X axis data while other columns are Y axis data The number of columns will depend on the number of plots in the Main Graph when this option is selected Note that this option saves all of the data in the Main Graph indicator not only the data that is currently visible Save Scan Data Use this option to saved scanned measurement data Selecting this option brings up the Save Scan Data dialog window shown in Fig 16 This dialog allows the user to select which components of the scan data to save The main array in the center of the dialog window will contain an entry for each Peak that was configured in the Peak Selection and Measurements array during the scanned measurement For each peak the SaveAmp checkbox selects whether to save amplitude data and the SavePR checkbox selects whether to save range data The field Prefix is used to specify a string that serves as the beginning of the filenames for the data files for that peak The Append Timestamp checkbox selects whether to append a timestamp to filenames Folder Path is the hard disk location where the data files will be saved 32 r Save Scan Data Dialog vi Save Scan Data SaveAmp SavePR SaveAmp SavePR Append Timestamp Folder Path D Ee Cancel Figure 16 The Save Scan Data dialo
94. timization by moving the stage and monitoring peak amplitude Peak optimization is accomplished using a hill climb algorithm i e the stage continues to move in a particular direction as long as the peak amplitude increases The first time peak amplitude decreases the stage reverses direction the second time it decreases the algorithm terminates 75 Called by Custom VIs called Labview VIs called Precision Ranging2 vi Scanning OFDR 2 2 vi Peak Cluster3 ctl Get Channel Assignments vi baseband2 vi NI_AALPro Ivlib Unwrap Phase vi NIL AALPro I vlib Real FFT vi NI_AALPro Ivlib Linear Fit vi NILAALPro Ivlib Inverse FFT vi NI_AALPro lvlib Inverse Complex FFT vi NILAALPro vlib FFT vi NI_AALBase lvlib Std Deviation and Variance vi Inputs 7 LV Class Name LVObjectRefNum Chart_PR Cluster error in no error Digital Filter Size Pts Digital NumEndpoints Array Peak Array Array Raw data Digital TrigDelay Outputs 4 LV Class Cluster Array Array Array Name error out Peak Array Out Peak selections Phases Description A reference to the Range Chart on the front panel of the main Scanning OFDR software application Input error cluster The number of points to selected at each peak location for the precision ranging calculation The number of endpoints to neglect during precision rang ing linear curve fit The Peak Selection and Measurements array passed from the main Scanning OFD
95. tom VIs called Labview VIs called Fourier Interpolation vi Resample vi WL vs Time vi None NI_AALPro Ivlib Real FFT vi NI_LAALPro Ivlib Inverse Real FFT vi NI_AALPro lvlib Inverse FFT vi NILAALPro lvlib FFT vi Inputs 2 LV Class Name Description Array Data Input data array to be interpolated Digital Interp Factor Factor by which to increase the number of data points in the data array Outputs 1 LV Class Name Description Array Interpolated Output interpolated data array Data VI description This VI interpolates a data array by zero padding in the Fourier domain The number of points in the data array is increased by a factor of Interp Factor 61 Called by Custom VIs called Generate X Axis vi Scanning OFDR 2 2 vi Plot Selection ctl OFDR Global vi Acquisition Parameters ctl Labview VIs called None Inputs 3 LVClass Name Description Cluster Aquisition Acquisition parameters cluster describing the raw data in Parameters memory Cluster error in no Input error cluster error Enum Plot Selection Selects the type of data to plot Outputs 3 LVClass Name Description Cluster error out Output error cluster Array X Axis X axis data for plot String X Axis Label X axis label for plot VI description This VI generates scaled X axis data for use in the main graph plots on the front panel of the main Scanning OFDR software application The content of the X axis data depends on the type of plot requ
96. ts array on the front panel of the main Scanning OFDR software application The peak amplitude calculation consists of numerical integration over a subset of the OFDR data ar ray centered at the peak locations specified by Location in the Peak Array and including a 73 number of points specified by Peak Area Pts Note that TrigDelay is passed as a parameter to this VI rather than reading OFDR Global vi because the global variable is the hardware value while data loaded from a file may use a different value 74 Called by Custom VIs called Peak Optimizer vi Scanning OFDR 2 2 vi Communication States ctl Labview VIs called None Inputs 6 LVClass Name Description Boolean Abort Op Aborts peak optimization Digital Amplitude Current measured peak amplitude value Digital Ctr2 Counter to track number of direction changes Cluster Data Cluster Queue message data cluster Two elements boolean Init to indicate first call and numeric Peak Opt to indicate which peak to optimize Cluster error in no Input error cluster error Digital Last Previous measured peak amplitude value Outputs 5 LVClass Name Description Digital Ctr2 Out Counter to track number of direction changes Boolean Done Indicates whether peak optimization process is complete Cluster error out Output error cluster Digital Last Out Current measured peak amplitude value Array Q States Queue state array VI description This VI manages peak op
97. tured by National Instruments The PCI 6115 resides inside the HP worksta 10 Table 2 Gain settings and bandwidths for the Thorlabs PDA10CS Photodetectors Gain Setting dB Bandwidth MHz 0 17 10 8 5 20 1 9 30 0 775 40 0 320 50 0 090 60 0 033 70 0 012 Table 3 Comparison of the PCI 6115 and PXIe 4492 DAQ boards Feature PCI 6115 PXIe 4492 ADC resolution 12 bits 24 bits Maximum sampling rate 10 MS s 204 8 kS s Input voltage range 42 V 10 V Number of analog inputs 4 8 Number of gain settings 8 2 Number of counters 2 0 Number of digital I O lines 8 0 Supports external clock Yes No Supports OFDR fiber optic switch control Yes No Supports confocal scanning Yes No tion and is accessed by the BNC 2110 connector block The PXIe 4492 resides in the PXIe 1073 chassis Only the PCI 6115 supports all of the features of the Scanning OFDR software and this DAQ board must always remain connected and functional The PXIe 4492 enables higher precision ranging measurements because it uses a 24 bit analog to digital converter ADC whereas the PCI 6115 uses a 12 bit ADC The PXIe 4492 has other significant limitations however and does not support all of the system features of the Scanning OFDR software application The most important lim itations to note are that the PXIe 4492 does not support use of an external clock and its maximum sampling rate is a factor of 50 smaller than that of the PCI 6115 Table 3 summarizes the r
98. ue for the current position Because the axis software limits are set in terms of an axis position changing the position label results in a shift of the physical location of the sotware limits if the stage position values of the sofware limits are not also shifted This VI will optionally perform the required software limit position shift in order to maintain the same physical location of the software limits 88 Signal Levels vi Called by Scanning OFDR 2 2 vi Custom VIs called OFDR Global vi Labview VIs called NI_AALBase lvlib Mean vi Inputs 2 LVClass Name Description Cluster error in no Input error cluster error Array Raw Data Input raw data array Outputs 4 LVClass Name Description Digital Aux Mean The mean data value on the Aux channel Cluster error out Output error cluster Digital P Mean The mean data value on the P channel Digital S Mean The mean data value on the S channel VI description This VI calculates the mean data values on the S P and Aux channels 89 Smoothing Filter vi Called by Confocal Plot Data vi Custom VIs called None Labview VIs called NI_AALPro Ivlib Real FFT vi NILAALPro Ivlib Inverse FFT vi NI_AALPro Ivlib Inverse Complex FFT vi NILAALPro vlib FFT vi Inputs 4 LVClass Name Digital Cutoff Array Data Cluster error in no error Digital Roll Off Width Outputs 4 LVClass Name Cluster error out Array Filter Window Array Filtered Data WaveformGraph Wa
99. veform Graph Description Width of the flat passband of the smoothing filter Input data array to be smoothed Input error cluster 1 e width of the Gaussian roll off of the smoothing filter Description Output error cluster The filter function that is multipled by the Fourier trans form of the input Data array Output data array with the smoothing filter applied VI description This VI applies a digital low pass filter applied to the supplied data input data array The filter is a dual sided amplitude only filter with a flat passband and Gaussian roll off The width of the flat passband is given by b Cutoff b and the 1 e width of the Gaussian roll off is given by b Roll Off Width b Frequency units are normalized relative to the sampling frequency 90 SS Drive Axis vi Called by Move SS Stage vi Custom VIs called OFDR Global vi Labview VIs called None Inputs 3 LVClass Name Description String Axis Axis selection Allowable values are A1 A6 for stage stack 1 or A7 A12 for stage stack 2 Boolean Direction Direction to move axis True moves clockwise false moves counterclockwise Cluster error in Input error cluster Outputs 1 LVClass Name Description Cluster error out Output error cluster VI description Moves the selected Seruga Seiki stage axis using the current settings for Drive Speed Start Up Speed Acceleration and Distance 91 Called by SS Go To Position vi Move SS

Scanning optical frequency domain reflectometer

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