2001 & 2011 User Manual RevB
Contents
1. 600 800 1000 1200 1400 Wavelength nm 10 1600 1800 2000 Fig 5 Response factor versus wave length for the Model 2011 Response Factor Vv 0 6 0 5 0 4 0 3 0 2 0 0 600 800 00 1200 1400 Wavelength nm 16 00 00 00 11 Vv Fig 6 NEP as a function of wavelength for Model 2001 at 104 Gain Setting 2 0 1 5 hie S 10 jas Lu a 0 5 0 0 200 400 600 800 1000 1200 Wavelength nm 12 Vv Fig 7 NEP as a function of wavelength for Model 2011 at 104 Gain Setting NEP pW Hz 600 1000 1400 1800 Wavelength nm 13 14 Operation Vv To check the two batteries 1 Turn on the photoreceiver using the power switch 2 Set the Low Frequency Adjust knob to DC 3 Set the Gain knob to 104x3 setting 4 Focus at least 100 pW of optical power on the detector or place the detector in front of a desk lamp The output should be greater than 7 V If it is not replace the batteries with fresh ones To replace the batteries The photoreceivers are shipped with two fresh 9 V batteries installed To avoid confusion about how2. much life is left in the batteries replace the batter ies on a monthly basis when the unit is in frequent use 1 Turn off the photoreceiver using the power switch 2 Use a Phillips head screw driver to remove the two screws on the back panel of the photoreceiv er see the figure in the Specifications 3 Remove the back panel 4 Replace the used 9 V batteries with fresh ones 5 Replace the back panel and the two screws 6 Recheck the battery level as described above Vv Tuning the position and frequency of the optical output 1 Use the 8 32 M4 tapped hole located on the base of the photoreceiver to mount it on an adjustment positioning device for alignment of the optical spot on the photodetector diode locat ed on the back side of the unit 2 Position the mounted photoreceiver in front of the focusing lens A simple 25 mm focal length biconvex singlet should be adequate for most applications 3 Turn on the optical beam 4 Connect the SMA port on the front of the pho toreceiver to a voltmeter 5 Align the detector to the beam until the output peaks on the voltmeter 6 Adjust the gain for optimal performance Refer to the discussion in Appendix 2 Electrical Output e Set the Low Frequency Adjustment knob to DC e Set the Gain knob to the full clockwise position e Set the Multiplier to X1 e Turn the Gain knob clockwise to increase it until you measure approximately 2 V on the vol
3. gt 100 kHz on most gain settings 1 20 Vv
4. Models 2001 and 2011 User s Manual Front End Optical Receivers Vv Vv v Is a registered trademark of 200110 Rev B New Focus Inc Warranty Contents Vv New Focus Inc guarantees its products to be free of defects for one year from the date of ship ment This is in lieu of all other guarantees expressed or implied and does not cover inci dental or consequential loss Warranty Introduction 4 Theory 6 Operation 14 Appendix 1 Optical Input 16 Appendix 2 Electrical Output 16 Specifications 19 Vv Introduction With the New Focus front end optical receivers you can measure optical signals conveniently and accurately These photoreceivers are optimized for versatility and efficient operation New Focus offers two different models to match your wavelength requirements Table 1 lists each model s character istics and specifications Both models have adjustable high and low pass filters as well as a 90 dB adjustable electronic gain range to allow shot noise limited detection at almost any optical power level from 1 pW to 10 mW The DC 30 setting prevents your signal from going off scale due to DC amplitude fluctuations Model 2001 has a noise equivalent power NEP of less than 1 pW VHz from 400 nm to 1060 nm on the 104 scale Model 2011 has an NEP of less than 0 5 pW VHz from 800 nm to 1600 nm on the 104 scale Both models maintain a static current drain of less than 1 mA which al
5. asure of the weakest optical signal and is a function of the wavelength The NEP as a function of wavelength on the 104 gain setting is shown in Fig 6 for Model 2001 and in Fig 7 for Model 2011 The NEP increases by a factor of approximately three for each full clockwise turn of the gain knob Both the photodiode and the circuit are powered from a 9 V supply provided by two 9 V alkaline batteries v Fig 1 Functional block diagram of the front end optical receiver photoreceivers Photodiode Adjustable gain stage 19000 Independently adjustable A 100 6 dB octave high and 10 low pass filters 1 with lt 90 phase shift A N va P SMA output Low noise i _ transimpedance Gain multiplier amplifier 3 1 v Fig 2 Responsivity of Model 2001 7 Responsivity A W 200 400 600 800 1000 1200 Wavelength nm Fig 3 Response factor versus wavelength for the Model 2001 Response Factor 0 4 0 3 0 2 0 0 200 400 600 800 Wavelength nm 1000 12 V 00 Fig 4 Responsivity of the Model 2011 Vv 06 0 4 Responsivity A W COZ
6. cor ner there will be significant attenuation at all fre quencies In addition the low frequency knob has a DC 30 setting This is a convenient setting for observing a small AC signal on a widely varying DC compo nent It will prevent your signal from going off scale due to DC amplitude fluctuations Note With the most sensitive gain setting 104 the maximum bandwidth is reduced to 20 kHz Gain Knob The overall gain is the product of the gain knob setting and the wavelength response factor V mW indicated on the front of the unit You can increase the gain by a factor of three by setting the Gain Multiplier Switch to x3 17 Fig 8 Setting the frequency response of the Front end Optical Receivers wo Response dB LN 6 dB octive Vv Roll off 6 dB octive 18 Log frequency Specifications Dimensional Performance Model 2001 Model 2011 H 1 78 45 2 i a M 8 32 M4 Thd Photodetector 2 25 57 1 UERR Lego Vv 5 17 131 2 124815 H 231688 4 Responsivity Peak 0 6 WW Conversion Gain Peak 1 1x107 VW NEP on the 104 scale 1 0 pw V Hz Responsivity Peak 0 8 AW Conversion Gain Peak 1 5x107 VW NEP on the 104 scale 0 5 pW VHz Accuracy Absolute 20 Range to Range Consistency 5 from 104 to 103 2 at other settings Frequency Response User definable from DC to
7. lows a pair of 9 V batteries to operate for at least 500 hours Table 1 Characteristics of the Front end Optical Receivers Vv Model Number 2001 2011 Wavelength Range 400 1060 nm 800 1600 nm Photodiode Material Silicon InGaAs Photodiode Size 0 81 mm2 0 09 mm2 Theory Vv A block diagram of Models 2001 and 2011 is shown in Figure 1 The photoreceiver consists of a photodiode followed by a transimpedance amplifi er two adjustable filters and a final gain multipli er Fig 1 The responsivity of the silicon photodi ode for the Model 2001 is shown in Fig 2 The response factor V mW which is a calibration term that converts measured electrical power to incident optical power at a specific wavelength is shown in Fig 3 for the Model 2001 The optical power striking the photodetector is equal to the voltage measured divided by the product of the gain knob setting multiplier factor 1 or 3 and the wavelength response factor see Appendix 1 Optical Input for a specific example Figs 4 and 5 show the responsivity and response factor for the InGaAs photodetector in the Model 2011 The noise performance of the Models 2001 and 2011 is determined by the setting of the first stage while the final gain stage simply scales the signal for ease of viewing The NEP is the amount of optical input power required for the output signal to just equal the output noise of the optical receiv er It is a me
8. tmeter 15 Appendix 1 Optical Input Appendix 2 Electrical Output 16 Vv The optical input power striking the photodetector is equal to the measured voltage divided by the product of the gain knob setting times the multi plier 1 or 3 times the wavelength response factor For example with these settings Gain knob 104 Gain multiplier x3 Response factor 0 25 Volts mW DC output voltage 2 V The optical input power therefore is equal to 2 V 104X3x0 25 270 nW The photoreceiver has three knobs a low frequen cy corner a high frequency corner and a gain knob as well as a gain multiplier switch Frequency Knobs The upper left knob adjusts the low frequency cor ner and the upper right knob adjusts the high fre quency corner The corner frequency is the fre quency where the response is down by 3 dB from its mid band value Fig 8 depicts the frequency response with a roll off at 6 dB octave below the low corner and above the high corner To obtain Vv signals over the full bandwidth set the low corner frequency knob to its full counterclockwise posi tion and set the high corner frequency knob to its full clockwise position The corner frequency increases by a factor of three with each full clock wise turn The photoreceivers have ten settings for each frequency corner creating a wide variety of frequency responses If the low frequency corner is set higher than or equal to the high frequency
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