The most common understanding of the optimal operation bias point is the bias condition for best receiver sensitivity. The receiver, in particular the TIA and the parasitics, will have an important impact on finding this optimal condition. The optimal bias for our 10G APD is around a multiplication gain of M=10. Using an appropriate TIA, our 10G APD achieves a receiver sensitivity of -28dBm. For the 2.5G APD the optimal multiplication gain is between M=10 and M=15. Using an appropriate TIA, our 2.5G APD achieves a receiver sensitivity of -35dBm.
The bias voltage corresponding to a multiplication gain of M=10 is found around 90% of the breakdown voltage.