Performance analysis of adaptive optics with a phase retrieval algorithm in orbital-angular-momentum-based oceanic turbulence links.

Recently, orbital angular momentum (OAM) beams have been applied in underwater optical communication (UWOC) to build a high-capacity communication link. However, a wave-front-sensitive OAM beam suffers significant distortion due to oceanic turbulence (OT), resulting in considerable intermodal crosstalk that degrades the UWOC performance. Herein, we propose and demonstrate an adaptive optics (AO)-based correction approach with a phase retrieval algorithm (PRA) to compensate for the distorted OAM beams induced by OT. In a simulation, an OT model with the random phase screen method is utilized. Two PRAs, the Gerchberg-Saxton algorithm (GSA) and the hybrid input-output algorithm (HIOA), are utilized to reconstruct the distorted phase-front of the OAM beam. The simulation results illustrate that the PRA-based AO approach can effectively compensate for the distorted OAM beam and improve the bit error rate performance in an oceanic channel. Additionally, the compensation performance of HIOA-based AO is superior to that of GSA-based AO in terms of convergence performance. This work verifies the feasibility and validity of a PRA-based AO approach in underwater turbulence optical communication and provides new insights into the OAM underwater communication system. (C) 2019 Optical Society of America