Performance of free space optical coherent communication with decision-aided carrier phase estimation

The performance of free space optical coherent communication with phase modulation is limited by both phase fluctuations and intensity scintillations induced by atmospheric turbulence. In this paper, we consider the effects of Gaussian phase fluctuations and Gamma-Gamma amplitude fluctuations, in addition to photodiode shot noise. Given temporal correlation of phase variations, decision-aided, maximum likelihood (DA-ML) phase estimator is employed in free space optical coherent communication system to improve system performance. Monte Carlo simulation results show that turbulent phase noise can be ignored with less than 0.1 dB signal-to-noise ratio penalty compared with no turbulence by using this phase estimation scheme. And intensity scintillations are the dominant impairment.