Statistical analysis of interferometric noise in optical ASK/direct detection systems

An eecient method for evaluating the error probability of optical ASK/DD systems subject to interferometric noise is presented. The receiver decision variable is statistically described by its moment generating function (mgf). The theoretical results, obtained with the aid of the new derived mgf, are in good agreement with experiment, employing directly modulated light sources, while the common used Gaussian statistics for the photocurrent yields larger power penalties. The analysis takes into consideration polarization statistics, photodetector shot noise, non-ideal extinction ratio, and receiver thermal noise. Error probabilities are calculated using the saddlepoint approximation which is numerically simple and gives accurate results.