Abstract

Atmospheric turbulence severely degrades the optical wavefront of a propagating beam, which greatly reduces the coupling efficiency of free-space optical (FSO) receivers. Among the various methods to mitigate the effects, the use of a multi-channel receiver is more convenient and economical. After passing through the multi-channel receiver, multiple single-mode fibers (SMFs) are output and need to be combined. In this paper, we propose photonic integrated coherent beam combiners based on multimode interference (MMI) and the stochastic parallel gradient descent (SPGD) algorithm, which avoids detecting the light out of each channel and adding the data signal in the electrical domain. First, we propose a 4-channel coherent beam combiner based on a ${4} \times {1}$ MM, and about 21 iterations of the SPGD algorithm are required to enhance the combined optical power to a maximum of 96%. Furthermore, we demonstrate a combination of 16 beams using five ${4} \times {1}$ MMIs, which requires 140 iterations to enhance the combined power to 89%. This study offers theoretical insights to enhance the integration of FSO communication systems.

© 2024 Optica Publishing Group

Free space optical communication receiver based on a spatial demultiplexer and a photonic integrated coherent combining circuit

Vincent Billault, Jerome Bourderionnet, Jean Paul Mazellier, Luc Leviandier, Patrick Feneyrou, Anaelle Maho, Michel Sotom, Xavier Normandin, Herve Lonjaret, and Arnaud Brignon
Opt. Express 29(21) 33134-33143 (2021)

Bandwidth and stability of the stochastic parallel gradient descent algorithm for phase control in coherent beam combination

Matts Björck, Markus Henriksson, and Lars Sjökvist
Appl. Opt. 60(15) 4366-4374 (2021)

Experimental demonstration of using divergence cost-function in SPGD algorithm for coherent beam combining with tip/tilt control

Chao Geng, Wen Luo, Yi Tan, Hongmei Liu, Jinbo Mu, and Xinyang Li
Opt. Express 21(21) 25045-25055 (2013)

Combining module based on coherent polarization beam combining

Yan Yang, Chao Geng, Feng Li, and Xinyang Li
Appl. Opt. 56(7) 2020-2028 (2017)

Modal decomposition of an incoherent combined laser beam based on the combination of residual networks and a stochastic parallel gradient descent algorithm

Fan Chen
Appl. Opt. 61(14) 4120-4131 (2022)