Performance analysis of an asymptotically quantum-limited optical DPSK receiver

An optical, direct-detection differential phase-shift keying (DPSK) receiver whose error probability is quantum-limited as the transmitting laser linewidth vanishes is analyzed. The receiver design is based on a binary equiprobable hypothesis test with doubly stochastic point process observations, the conditional random rates of which depend on the transmitting laser phase noise, which is modeled as a Brownian motion. The receiver structure consists of a simple delay-and-sum optical preprocessor followed by a photoelectric converter and an integrate-and-dump circuit. Upper and lower bounds on the receiver bit error rate are derived by developing bounds on the conditional rates of the point process, and it is shown that the error probability bounds converge to the true value as the transmitting laser linewidth decreases. Bounds on the power penalty are computed for parameters corresponding to existing semiconductor injection lasers, and are seen to be less than the limiting power penalty for the balanced DPSK receiver