Fade statistics associated with a space/ground coherent receiver array

Laser-satellite communication system are subject to signal fading below a prescribed threshold value owing primarily to optical scintillations associated with the received signal, regardless of pointing in errors. The probability of fade associated with a downlink laser-satellite communication system is calculated here as a function of threshold intensity below the mean intensity of a Gaussian-beam wave incident on a coherent equal-gain (EG) receiver array. Previous theoretical studies and experimental data reveal that the mean carrier-to-noise ratio for an EG array receiver system improves greatly over that of a conventional single aperture monolithic coherent detection system. The present theoretical analysis illustrates there is also a significant decrease in the fractional fade time for an EG optical array receiver system with two or more receivers spatially separated by more than the intensity correlation length of the received optical signal.