Robust free space optical communication receiver based on a spatial mode demultiplexer and a silicon photonic coherent combining circuit

Mitigation of atmospheric turbulence is a major challenge in optical wireless communication, especially for optical feeder links. In this paper, we present a free space optical (FSO) mode diversity receiver, based on a spatial demultiplexer and a silicon photonic coherent combiner to reduce the atmospheric turbulence deleterious effects. We simulate the spatial light distribution in the ground receiver aperture for a use case consisting of a FSO link from a GEO satellite. We then generate experimentally wavefronts corresponding to the spatial light distribution for that use case with a wavefront emulator, and we compare the collection efficiency of the proposed mode diversity receiver with a FSO single mode fiber (SMF) receiver. The proposed FSO receiver outputs a signal much more stable as the system is resilient to energy redistribution among higher order spatial modes.