Laser Phase Noise in Coherent and Differential Optical Transmission Revisited in the Polar Domain

We revisit the treatment of laser phase noise, with particular application to coherent and differential phase-shift keyed (PSK) systems, developing a considerably simplified yet very accurate analysis based on the phase-noise exponent commutation (PNEC) premise that the receive filtering may be effectively applied in the polar (angular) domain and treating for the first time arbitrary transmit pulses (e.g., return to zero) and optical filter responses (still without intersymbol interference). The PNEC concept directly implies that the angle of the PSK and differential PSK decision statistic is Gaussian distributed, which is verified numerically as very accurate, by means of importance-sampling-based Monte Carlo simulations.