**edited as per suggestions in elog:2420
The dark noise of IG22X2000T9(serial: X8906 and X8905), Extended InGaAs photodiodes was measured. A low pass sallen key filter(using OP27) with a gain of +1 and cut off frequency of 1Hz was used to provide the bias voltage to the photodiode. A transimpedance amplifier(using OPA140, refer elog:2416 for noise spectrum of TIA) with a gain of 5.1k was used to convert the output current of the photodiode to voltage. The input range was maintained at -50 dBVpk during the measurement.
A bias voltage of 1.017 V was provided and the output voltage across the transimpedance amplifier was observed to be as follows:
X8906: -0.030V, which implies that the dark current was -5.887uA.
X8905: -0.097V, which implies that the dark current was -19.01uA.
Attachment 1: Setup representation
Attachment 2: Experimental Setup. It was made sure that the cables are free from any tension. Connections were made using BNC connectors. The transimpedance amplifier and sallen key filter were placed in a box and were not in direct contact with the optical bench. During measurement data was taken with a linewidth of 125mHz(was increased logarithmically for subsequent measurements, since measurement was taken in parts) with 200 averages for each set.
Attachment 3: Dark noise plot. The data was taken for X8906 for 5 different bias voltages. The input range was maintained at -50 dBVpk during the measurement. It was observed that dark noise decreases with decrease in bias voltage.
Attachment 4: Dark noise plot. The data was taken for X8905 for 4 different bias voltages. The input range was maintained at -46 dBVpk during the measurement. It was again observed that the dark noise decreases with a decrease in bias voltage.
***** The noise is observed very low for a 0V bias for both the photodiodes below 10kHz. It was observed that noise is high above 10kHz at all the bias voltages for both the series.
Attachment 5: Dark Current plot for both X8905 and X8906 series of photodiodes.
Attachment 6: Dark Current Density for both X8905 and X8906 series.
Although being made of the same material both the photodiodes have some difference in their dark current. It was observed that the photodiodes are very noisy at room temperature. I think they will deliver better performance at low temperatures.
Attachment 7: The 1/f noise was observed at 10Hz for both the series of photodiodes.
Attachment 8: Zip file to re-create the data.