Control circuits for dynamically biased avalanche photodiodes

Abstract

Method and apparatus for maximizing the output of a dynamically biased avalanche photodiode (APD). The output of the APD is amplified. A feedback loop comprising a phase shifter measures the RF power of the amplified output and adjusts the phase of the AC signal which is used to dynamically bias the APD until the output power is maximized. The AC signal is also split into out of phase signals, thereby substantially canceling out the bias current injected into the APD output, leaving only the desired amplified optical output signal. The monitoring and tuning of the AC dynamic bias can eliminate phase drift over time, as well as other non-ideal effects that can occur, such as those due to temperature changes or device aging effects.