Receiver design for underwater wireless optical communication link based on APD

In this paper, we present a gain control scheme of receiver based on avalanche photodiodes (APDs) for underwater wireless optical communication links. We first derive the approximate expression of optimal gain of APD. Then based on beam-spread function, a closed-form expression of relationship of optimal gain of APD, link range and receiver offset distance is derived. Then a self-adaptive gain control scheme is designed to keep the gain of receiver as optimal gain when the receiver deviates unpredictably. We also evaluate the dynamic range of receiver gain. Our results are beneficial for receiver design and link reliability improvement.