Spatial polarization phase shift keying for high-capacity coherent free-space optical communication

Enhancing the information capacity of a light beam per unit of bandwidth has been a goal sought by researchers in coherent free-space optical communication (CFSOC). Nonetheless, atmospheric turbulence induces fluctuations in the beam's polarization state and phase distortion. By combining polarization multiplexing and phase modulation, we propose a spatial polarization phase shift keying (SPPSK) technique. It dramatically increases the data capacity of the CFSOC system. In addition, the vectorial adaptive optics (V-AO) system is designed to correct polarization and phase aberrations. It is intended to reduce interference resulting from atmospheric turbulence. We effectively exhibit simulation experiments under turbulent channel conditions. The result shows the potential of using SPPSK to achieve a ∼20X increase in data capacity for the CFSOC link based on a single beam. The V-AO effectively corrects the polarization aberration of the beam. It decreases the BER and enhances communication performance. Hopefully, this research can provide a reference basis for developing future high-capacity laser communication systems.