Effects of atmospheric compensation techniques on the performance of synchronous receivers

We present recent studies on the impact of atmospheric turbulence on free-space links using either synchronous or nonsynchronous detection. We compare options for atmospheric compensation, including phase compensation and diversity combining techniques. We consider the effects of log-normal amplitude fluctuations and Gaussian phase fluctuations, in addition to local oscillator shot noise, for both passive receivers and those employing active modal compensation of wave-front phase distortion. We compute error probabilities for M-ary phase-shift keying, and evaluate the impact of various parameters, including the ratio of receiver aperture diameter to the wave-front coherence diameter, the number of diversity channels, and the number of modes compensated.