154411 revB 12GHz revA.fm
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1. 80 5903 Support is also available by fax and email Fax 408 987 3178 Email techsupport newfocus com We typically respond to faxes and email within one business day In the event that your photoreceiver malfunctions or becomes damaged please contact New Focus for a return authorization number and instructions on shipping the unit back for evaluation and repair Please have the product s serial number and your original purchase order information available when you call 12 GHz Photoreceivers Customer Service 13 14 Customer Service Appendix Optical Fiber Performance Single mode optical fiber can provide low loss and low distortion if attention is paid to a few important details First if more than one mode is allowed to propagate in a step index fiber the bandwidth will be degraded to approximately cn B 2 2L NA Where c is the speed of light in free space mis the index of the core Zis the length of the fiber and NA is the numerical aperture of the fiber Modal distortion can be eliminated by using a fiber with a core small enough that only a single mode will propagate In this case the bandwidth of the fiber will be limited by material dispersion which is a property of the glass used in the fiber core In this limit the bandwidth is approximately 1 Pret 3dB 2LMAA where Z is the fiber length in kilometers Mis the material dispersion in ps nm x km and Ad is the linewidth of the optic2. USER S GUIDE 12 GHz Amplified Photorecelvers Models 1544 A amp 1554 A Including multimode 50 option These photoreceivers are sensitive to electrostatic discharges and could be permanently damaged if subjected even to small discharges Ground your self adequately prior to handling these receivers or making connections A ground strap provides the most effective grounding and minimizes the likelihood of electrostatic damage CAUTION V New Focus A Newport Corporation Erand 3635 Peterson Way Santa Clara CA 95054 USA phone 408 980 5903 fax 408 987 3178 e mail techsupport newfocus com www newfocus com Warranty Newport Corporation guarantees its products to be free of defects for one year from the date of shipment This is in lieu of all other guarantees expressed or implied and does not cover incidental or consequential loss Information in this document is subject to change without notice Copyright 2012 2001 1998 Newport Corporation All rights reserved The New Focus logo and symbol are registered trademarks of Newport Corporation Document Number 154411 Rev B Contents Operation iO dUCHon ss sodo rieti ili Handling Precautions Connecting the Power Supply and Bias Microwave Connection and Set up Connecting the Receiver to the Optical Input Troubleshooting Testing the Photodiode Checking the DC Offset Volt
3. age Basic Optical Test ssl policies des Characteristics Photoreceiver CharacteristicS Bias Monitor Characteristics KESDONSIVILY eee kaka ee ok anan ed a ka te e ia n Customer Service Technical Support DORVICE st bw Mes ki aa owes Appendix l Optical Fiber Performance Appendix II Microwave Connectors Appendix III Inside the Photoreceiver 12 GHz Photoreceivers Contents e 3 4 e Contents Operation Introduction High speed measurements down to a few microwatts are easy with the Models 1544 A and 1554 A photoreceiver modules These modules convert optical signals to electronic signals in effect giving every high speed high frequency instrument in your lab an optical input In earlier low frequency LF versions we used an external DC block to achieve low frequency cutoffs of 10 KHz In the current A versions we eliminated the external blocking capacitor achieving the 10 KHz cutoff with an internal capacitor In the standard models the optical signal is delivered to the Schottky photodiode through a single mode optical fiber in the 50 models the signal is delivered through a 50 125 um multimode fiber The small size of the module allows you to connect it directly to your test instrument or amplifier This eliminates the need to follow the photoreceiver with coaxial cable which can seriously distort picosecond pulses and a
4. al source in nm This bandwidth limitation can be ignored for glass fibers less than 10 meters in length but can be serious for longer fibers and spectrally broad sources Palais C J Fiber Optic Communications Prentice Hall Inc Englewood Cliffs NJ 1984 12 GHz Photoreceivers Appendix l Optical Fiber Performance 15 16 e Appendix Optical Fiber Performance Appendix Il Microwave Connectors The performance you obtain from the Models 1544 A and 1554 A photoreceivers depends largely on the instruments you use to measure their outputs and how the connections are made to the instruments Connect the male connector of the photoreceiver directly to the female connector of the instrument For the low frequency version be sure to include a DC block between the receiver and the instrument If you need to use an adapter make sure it is designed for your frequency range of interest The following table lists a few connectors and the frequency ranges in which they may be used For more information request Application Note 1 If you use an intervening coaxial cable select a cable with sufficiently low loss in the frequency range of interest Tene peace n New Focus also offers the following adapters Model 1225 Male SMA to Female BNC Model 1226 Female SMA to Male BNC Model 1227 40 GHz Flex Cable Female K to Male K 12 GHz Photoreceivers Appendix Il Microwave Connectors 17 18 e Appendix Il Microwave Connecto
5. cluded with the receiver use the appropriate cable for your power supply Connecting to a New Focus power supply Use the cable with the two round microconnectors Connect one end of the cable to one of the power supply s 300 mA outputs Connecting to another power supply Use the cable with the round microconnector on one end and three banana plugs on the other end Be careful to connect the banana plugs to the power supply as follows connect the red plug to a well regulated 15 V 200 mA source connect the black plug to a 15 V 200 mA source connect the green plug to the common ground of the two sources Connect the bias monitor port to a voltmeter and observe the voltage level This voltage is the DC offset plus dark current This dark voltage should be less than 5 mV If you are coupling light into a fiber use the voltmeter to monitor the photocurrent to help optimize the coupling Microwave Connection and Set up 1 12 GHz Photoreceivers Connect the photoreceiver module s microwave connector to a test instrument that has a 50 Q input such as an oscilloscope or spectrum ana lyzer or to another 50 Q load If necessary use a high frequency cable best performance is achieved without a cable To avoid connector damage and signal distortion be sure that the cable and the instrument you intend to connect to the module have compatible connectors See Appendix II Microwave Connectors on page 17 for a list
6. equency Cutoff 10 kHz 10 kHz Max Conversion Gain 850 V W 850 V W 750 A W MM version 750 A W MM version Typical Max Responsivity 0 9 A W 0 9 A W 0 8 A W MM version 0 8 A W MM version Transimpedance Gain 1000 V A 1000 V A 24 pW JHz 24 pW JHz Minimum NEP 27 MM version 27 MM version cw Saturation Power 3 mW Maximum Pulse Power 3 mW Detector Material Type InGaAs Schottky Detector Diameter 25 um Power Requirements 15 V lt 200 mA Optical Input Connector FC PC Electrical Output Wiltron K 12 GHz Photoreceivers Characteristics 11 Bias Monitor Characteristics Model 1544 A 1554 A Output Impedance 10 kQ 10 kQ Bandwidth 50 kHz 50 kHz Responsivity A graph of the typical and predicted responsivity of the Models 1544 A and 1554 A is shown below Figure 2 Responsivity Responsivity vs wavelength from 0 0 52 AW for a Model over the range of 1544 A 950 970 MIM b Model 1554 A 300 500 700 900 1100 1300 1500 1700 Wavelength nm 12 e Characteristics Customer Service Technical Support Service Information and advice about the operation of any New Focus product is available from our applications engineers For quickest response ask for Technical Support and know the model and serial number for your product Hours 8 00 5 00 PST Monday through Friday excluding holidays Toll Free 1 866 NUFOCUS 1 866 683 6287 from the USA amp Canada only Phone 408 9
7. of compatible connectors Operation 7 Connecting the Recelver to the Optical Input 8 e Operation To avoid signal distortion the optical fiber used to deliver the optical signal to the photoreceiver should be single mode at the operating wavelength and the cable length should be no longer than necessary If you have the multimode 50 model use 50 125 um fiber 1 Beforeconnecting the photoreceiver measure the power in the fiber to ensure it is within the safe operating range For a pulsed input determine the maximum peak power You may want to use the New Focus Model 2011 FC 200 kHz Photoreceiver for this purpose it has a higher maximum pulse power and has the sensitivity to aid in fiber alignment 2 Connectthe fiber optic cable to the fiber optic input Troubleshooting Testing the Photodiode The photodiode can be damaged by electrostatic discharge or excessive optical power which can lead to an increased dark or offset voltage A damaged photodiode can result in a degraded responsivity and frequency impulse response See Checking the DC Offset Voltage below Other problems such as a damaged amplifier are more difficult to diagnose If the response from your receiver is lower than you expect contact New Focus to arrange for a repair see Customer Service on page 13 Checking the DC Offset Voltage 1 With no light on the photodetector turn the detec tor on 2 Useavoltmete
8. r to measure the Bias Monitor output voltage This voltage is the DC offset plus dark current 3 Ifthe output is gt 5 mV then the detector is probably damaged and will need to be returned to New Focus If the output is lt 5 mV then perform the Basic Optical Test described below 12 GHz Photoreceivers Troubleshooting 9 Basic Optical Test To quickly test the photodiode in your receiver run this simple DC optical test 1 2 Turn the receiver on Using a voltmeter or oscilloscope measure the output voltage from the Bias Monitor on the front panel of the bias supply With no light on the detector the Bias Monitor voltage should be lt 5 mV Illuminate the photodetector With the voltmeter or oscilloscope you should observe a DC output voltage If you know the optical power and wavelength you can calculate the expected output voltage W using the expression Vu FR Re G where P is the input optical power watts Ris the photodetector s responsivity A W and Gis the amplifier s transimpedance gain V A The gain of the bias monitor port is 1000 V A If the output voltage is low then contact New Focus to arrange for a repair see Customer Service on page 13 10 e Troubleshooting Characteristics Photoreceiver Characteristics Model 1544 A 1554 A Wavelength Range 800 1650 nm 500 1650 nm multimode versions 800 1650 nm 550 1330 nm 3 dB Bandwidth 12 GHZ 12 GHZ Low Fr
9. rs Appendix Ill Inside the Photoreceiver Figure 3 Simplified schematic of the Models 1544 A amp 1554 A photorecelver modules A gold plated microwave housing inside the photoreceiver module contains the high frequency circuitry This housing is bolted to a printed circuit board which regulates the bias for the photodiode and amplifies the DC photocurrent for the monitor port The optical signal is brought from the front panel connector to the microwave housing with 9 um core fiber Although the material and modal dispersion per unit length of this fiber can be high at certain wavelengths there is no degradation in frequency response since the fiber is only 0 1 meters long The multimode version uses a 50 125 um fiber and a lens to image the core onto the 25 um detector active area Microwave Microwave Housing Output Photodiode gt Bias M onitor 12 GHz Photoreceivers Appendix Ill Inside the Photoreceiver e 19 20 e Appendix III Inside the Photoreceiver
10. ttenuate microwave signals Both the Model 1554 A and the 1544 A have a negative conversion gain due to the inverting amplifier used If you are using an oscilloscope and you want a positive output use the scope s inverting x 1 function 12 GHz Photoreceivers Operation 5 Figure 1 Models 1544 A amp 1554 A photorecelver modules Bias monitor port output is equal to photodiode current times 1000 Q for 1 mV uA Output K connector 2 25 a Power switch 2 00 50 8 3 14 79 8 FC PC connector Power for fiber optic input connector Handling Precautions Whenever handling the photoreceiver make sure to follow these precautions Follow standard electrostatic discharge precautions including grounding yourself prior to handling the detector or making connections even small electrostatic discharges could permanently damage the detector A ground strap provides the most effective grounding and minimizes the likelihood of electrostatic damage Do not over torque the microwave K connector Excessive torque can damage connectors Make sure the optical connector is clean and undamaged before connecting it to the detector module Connecting the Power Supply and Bias 1 6 Operation Prior to handling the detector ground yourself with a grounding strap to prevent electrostatic damage to the receiver Connect the power cable to the power supply Two power cables were in
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