A novel 2-D adaptive Wiener-filter-based algorithm for mitigation of atmospheric turbulence effects in deep-space optical communications

Atmospheric turbulence along with the background noise is a major limiting factor in a typical free space optical communication link. As compared to terrestrial links, Earth based optical receivers operating in near-space and deepspace communication links are affected more severely by the turbulence, as these systems have to look directly towards the sky to maintain line of sight with the transmitter. Especially during the daytime when the optical turbulence effect is at its peak and atmospheric seeing is the worst, the presence of the diffuse background light from the sky severely degrades the performance of an optical communication receiver. In this paper, we analyze the origin of the turbulence and simulate turbulence effects in an Earth-space optical channel. The photon counting focal plane detector arrays obeying Poisson statistics are employed in the receiver. We develop the concept of a pre-processor for optical communication receivers, which employ 2-D adaptive Wiener filter based practical algorithms for mitigation of turbulence and background noise effects. It is shown through simulations that for photon counting receivers observing Poisson distributed optical signals, performance improvements of 4-7 dB can be achieved under adverse conditions. This performance improvement is not only significant but the implementation of the pre-processor is also cost effective and practical.