Tian Qinghua

Review of coded modulation free space optical communication system

This paper presents a constructive discussion and inclusive review on advancements in the coded modulation free-space optical (FSO) communication system and corresponding techniques. These techniques mainly include channel model, forward error correction (FEC) and modulation schemes. Firstly, a complete view of FSO system is presented which contains the description, the current research situation along with the advantages over the traditional radio frequency (RF) wireless communication and fiber optical communications. Then, the channel model, FEC, modulation schemes and complete system of coded modulation FSO are analyzed successively. At last, the review work of coded modulation FSO system is summarized and further improvements are prospected.

A new version of Stochastic-parallel-gradient-descent algorithm (SPGD) for phase correction of a distorted orbital angular momentum (OAM) beam

Atmospheric turbulence limits the performance of orbital angular momentum-based free-space optical communication (FSO-OAM) system. In order to compensate phase distortion induced by atmospheric turbulence, wavefront sensorless adaptive optics (WSAO) has been proposed and studied in recent years. In this paper a new version of SPGD called MZ-SPGD, which combines the Z-SPGD based on the deformable mirror influence function and the M-SPGD based on the Zernike polynomials, is proposed. Numerical simulations show that the hybrid method decreases convergence times markedly but can achieve the same compensated effect compared to Z-SPGD and M-SPGD.