Experimental investigation of noise immunity in noncoherent spatially separated reception of optical signals in the atmosphere

An experimental investigation was made of the noise immunity in noncoherent spatially separated reception of optical signals in a turbulent atmosphere over a 500 m long slightly inclined path. A comparative analysis was made between the noise immunity of various methods of combining signals from separate channels when using spatially separated reception, namely: discrete (majority) summation, automatic selection of the channel with the highest transmission coefficient, and coherent (linear) summation in the case of noncoherent reception. The probability distribution laws of the received signals were studied for these methods of combining the channels. Measurements were made of the error reception probability as a function of the signal-to-noise ratio and degree of atmospheric turbulence, and the results were compared with theoretical estimates.