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High Sensitivity APD Optical Receiver

High Sensitivity APD Optical Receiver

The 7510-1 hybrid is a high gain, low noise optical receiver employing an avalanche photodiode (APD) with a nominal bandwidth of 100 MHz and superior dynamic range. It incorporates a thermo-electric cooler to help maintain detector performance at temperature extremes. This note discusses the performance, considerations, function and physical constraints of each pin.

The sensor’s main purpose is to enable the user to compensate the voltage bias of the APD for temperature, and takes advantage of the fact that biased with a constant current, the voltage across a diode will vary by about -2.5mV per degree C. The diode should be biased with very low current (micro amps) to prevent self heating. Biasing the diode with 301K Ohm resistor connected to a 2.5V reference voltage is sufficient where the room temperature voltage will be about 0.37V (this voltage will be stated on test sheet). This node should be carefully buffered by a non inverting op-amp to prevent noise injection and loading.