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12-GHz Photoreceivers

Troubleshooting • 11

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

With no light on the photodetector, turn the
detector on.

Use a voltmeter to measure the Bias Monitor
output voltage. This voltage is the DC offset plus
dark current.

If the output is >5 mV, then the detector is
probably damaged and will need to be returned to
New Focus.

If the output is <5 mV, then perform the Basic
Optical Test described below.

1580-A Rcvr revA.fm Page 11 Friday, May 10, 2002 3:07 PM

Содержание 1580-A

Страница 1: ...aged 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 5215 Hellyer Ave San Jose CA 95138 1001 USA phone 408 284 6808 fax 408 284 4824 e mail contact newfocus com www newfocus com ...

Страница 2: ... 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 2002 2001 1998 New Focus Inc All rights reserved The and logos and NEW FOCUS Inc are registered trademarks of NEW FOCUS Inc Document Number 158001 Rev A ...

Страница 3: ...necting the Receiver to the Optical Input 8 Characteristics 9 Photoreceiver Characteristics 9 Bias Monitor Characteristics 10 Responsivity 10 Troubleshooting 11 Testing the Photodiode 11 Checking the DC Offset Voltage 11 Basic Optical Test 12 Customer Service 13 Technical Support 13 Service 13 Appendix I Microwave Connectors 15 Appendix II Inside the Photoreceiver 16 ...

Страница 4: ...4 Contents NEW FOCUS Inc ...

Страница 5: ...odels 1580 LF 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 The Model 1580 A uses a GaAs PIN photodiode designed for high responsivity in the 780 870 nm wavelength range The internal 62 5 µm multimode fiber which delivers light to the photodiode p...

Страница 6: ...e 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 Prior to handling the detector ground yourself with a grounding strap to prevent electrostatic damage to the rece...

Страница 7: ... the common ground of the two sources 3 Connect the bias monitor port to a voltmeter and observe the voltage level on the voltmeter 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 Connect the photoreceiver mo...

Страница 8: ...er 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 Connect the fiber optic cable to the fiber optic input ...

Страница 9: ... minimum Low Frequency Cutoff 10 kHz Rise Time 34 ps Conversion Gain 400 V W Responsivity 0 4 A W Transimpedance Gain 1000 V A Output Impedance 50 Ω Noise Equivalent Power NEP 50 pW cw Saturation Power 1 5 mW Maximum Pulse Power 1 5 mW Detector Material Type GaAs PIN Input Fiber 62 5 µm multimode Optical Input Connector FC PC Electrical Output Connector Wiltron K Power Requirements 15 V 200 mA Hz ...

Страница 10: ...f the typical and predicted responsivity of the Model 1580 A is shown below Figure 2 Responsivity vs wavelength for Model 1580 A Model 1580 A DC Gain 1 mV µA DC Offset max 5 mV Output Impedance 10 kΩ Bandwidth 50 kHz 0 1 0 0 2 0 3 0 4 0 5 700 600 800 900 Wavelength nm Responsivity A W ...

Страница 11: ...uch 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 detector on 2 Use a voltmeter to measure the Bias Monitor output voltage This voltage is the DC offset plus dark current 3 If the o...

Страница 12: ...e 5 mV 3 Illuminate the photodetector 4 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 Vout using the expression Vout Pin R G where Pin is the input optical power watts R is the photodetector s responsivity A W see page 10 and G is the amplifier s transimpedance gain V A The gain o...

Страница 13: ...s 8 00 5 00 PST Monday through Friday excluding holidays Toll Free 1 866 NUFOCUS 1 866 683 6287 from the USA Canada only Phone 408 284 6808 Support is also available by fax and email Fax 408 980 8883 Email techsupport newfocus com We typically respond to faxes and email within one business day Service In the event that your photoreceiver malfunctions or becomes damaged please contact New Focus for...

Страница 14: ...14 Customer Service NEW FOCUS Inc ...

Страница 15: ...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 Connector Frequency Range Compatibility BNC DC 2 GHz SMA DC 18 GHz W...

Страница 16: ...ted 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 62 5 µm core multimode fiber Figure 3 Simplified schematic of the Model 1580 A photoreceiver module Microwave Housing Photodiode Microwave Output Connector V V Bias Monitor Instru...

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