Adaptive-optics-based turbulence mitigation in a 400 Git/s free-space optical link by multiplexing Laguerre-Gaussian modes varying both radial and azimuthal spatial indices

Xinzhou Su*, Zile Jiang, Yuxiang Duan, Huibin Zhou, Hao Song, Kai Pang, Cong Liu, Kaiheng Zou, Runzhou Zhang, Haoqian Song, Nanzhe Hu, Moshe Tur, Alan E. Willner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

In general, atmospheric turbulence can degrade the performance of free-space optical (FSO) communication systems by coupling light from one spatial mode to other modes. In this Letter, we experimentally demonstrate a 400 Gbit/s quadrature-phase-shift-keyed (QPSK) FSO mode-division-multiplexing (MDM) coherent communication link through emulated turbulence using four Laguerre Gaussian (LG) modes with different radial and azimuthal indices (LG10, LG11, LG−10, and LG−11). To mitigate turbulence-induced channel cross talk and power loss, we implement an adaptive optics (AO) system at the receiver end. A Gaussian beam at a slightly different wavelength is co-propagated with the data beams as the probe beam. We use a wavefront sensor (WFS) to measure the wavefront distortion of this probe beam, and this information is used to tune a spatial light modulator (SLM) to adaptively correct the four distorted data-beam wavefronts. Using this adaptive-optics approach, the power loss and cross talk are reduced by ∼10 and ∼18 dB, respectively.

Original languageEnglish
Pages (from-to)6452-6455
Number of pages4
JournalOptics Letters
Volume48
Issue number24
DOIs
StatePublished - 15 Dec 2023

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