<title>Carrier-to-noise ratio gain factor of coherent array detection system for laser radar and communications under different conditions of atmospheric turbulence</title>

Abstract

A coherent array detection system can improve the heterodyne mixing efficiency compared to a conventional coherent detection system which is limited by the finite transverse coherence length of received laser field due to atmospheric turbulence for laser radar and communications. This implies a gain factor in the mean power of the IF signal from the coherent array detection system compared to the conventional coherent detection system even though the two systems receive the same power of laser signal. This gain factor is actually the mean carrier-to-noise ratio (CNR) gain factor of the coherent array detection over the conventional coherent detection if the two systems have the same local oscillator and are shot noise-limited of the local oscillator. But the mean CNR gain factor depends on the conditions of atmospheric turbulence. This paper describes the theoretical analyses of the mean CNR gain factor for the coherent array detection system under different conditions of atmospheric turbulence which include weak, strong, and saturation conditions, corresponding to the lognormal, the K, the I-K, the negative exponential (Rayleigh for amplitude), and the gamma (Nakagami for amplitude) distributions for the laser intensity fluctuations.