A simplified non-Gaussian approach to digital optical receiver design with avalanche photodiodes: theory

A simplified theory of avalanche photodiode receiver sensitivity is presented in which the non-Gaussian nature of the avalanche multiplication process is taken into account. The theory predicts more accurately than a Gaussian theory the optimum avalanche gain and decision threshold and gives simple results for the influence of background photocurrent or dark current on receiver sensitivity, optimum gain, and threshold. For purposes of comparison, a parallel derivation using the Gaussian approximation for both the avalanche and receiver noises is given where simple expressions for the optimum avalanche gain and threshold settings are derived