Orbital-angular-momentum free-space optical communication via the azimuthal phase-shift

TL;DR

This paper introduces a novel OAM-based free-space optical communication method using azimuthal phase-shift, demonstrating high resilience to atmospheric turbulence and enabling more reliable high-bandwidth optical links.

Contribution

The paper proposes and experimentally demonstrates a new OAM-APSK scheme combined with digital holographic mode sorting that significantly improves turbulence resilience in free-space optical communication.

Findings

Achieved high signal-to-noise ratios under strong turbulence

Maintained low modal crosstalk beyond existing methods

Enabled reliable OAM communication in adverse atmospheric conditions

Abstract

Free-space optical communication using the orbital angular momentum (OAM) of light has garnered significant interest lately due to the potentially vast bandwidth intrinsic to the infinite Hilbert space of OAM modes. Unfortunately, OAM light beams suffer from serious distortions due to atmospheric turbulence (AT) that has become a dominant factor limiting the advance of OAM-based free-space communication. Here we propose and demonstrate a free-space communication scheme---using OAM beams and their azimuthal-mode phase-shift for keying (OAM-APSK)---which is resilient to AT-induced distortions. Combined with a digital holographic mode sorting (DHMS) technique, the proposed approach is able to achieve high signal-to-noise ratios and to maintain low modal crosstalk, even for extremely strong turbulence conditions, with magnitudes significantly beyond existing AT mitigation methods. The demonstrated OAM-APSK and DHMS schemes may now open up a great avenue for OAM-based free-space optical communication that could elegantly resolve the long-standing challenge imposed by atmospheric turbulence.