OAM Mode Selection and Space-Time Coding for Turbulence Mitigation in FSO Communication

TL;DR

This paper proposes a mode selection criterion and space-time coding scheme for OAM-based FSO communication systems to mitigate atmospheric turbulence effects, significantly improving error performance especially under strong turbulence conditions.

Contribution

It introduces a novel OAM mode selection criterion and a space-time coding scheme tailored for turbulence mitigation in 2x2 MIMO FSO systems, enhancing reliability.

Findings

Error probability is minimized under weak turbulence.

Significant coding gains are achieved in strong turbulence.

The proposed methods effectively absorb turbulence-induced penalties.

Abstract

Free space optical (FSO) communications using orbital angular momentum (OAM) modes has recently received a considerable interest. Propagating OAM modes through free space may be subject to atmospheric turbulence (AT) distortions that cause intermodal crosstalk and power disparities between OAM modes. In this article, we are interested in 2x2 multiple-input multiple-output (MIMO) FSO coherent communication systems using OAM. We propose a selection criterion for OAM modes to minimize the impact of AT. To further improve the obtained performance, we propose a space-time (ST) coding scheme at the transmitter. Through numerical simulations of the error probability, we show that the penalty from AT is completely absorbed for weak AT and considerable coding gains are obtained in the strong AT regime.