Diversity Reception for Deep-Space Optical Communication Using Linear Projections

A novel spatial diversity receiver for deep-space optical communication links is proposed. Using digital micromirror devices, the receiver optically computes linear projections of the turbulence-degraded focal-plane signal distribution onto an orthogonal binary basis. By using such projections, an estimate of the signal distribution is computed and updated adaptively to follow the time variations of the signal distribution. The estimate is used to perform selection combining, i.e., to select the portions of the focal plane that contain significant energy for symbol detection. The proposed receiver is less complex, requires less high-speed analog electronics and has lower preamplifier noise than a comparable multiple-detector array receiver. On the other hand, the proposed receiver requires more optical components and additional digital hardware to control the micromirror devices. Symbol error-rates (SERs) are simulated on a photon-counting channel and performance improvements about 2–5 optical decibels (dBo) over a conventional single-detector receiver are obtained at SER = $\hbox{10}^{-2}$.