基于MIMO模式分集相干接收的自由空间光通信大气湍流补偿技术研究  

Free-Space Optical Communication Atmospheric Turbulence Compensation Based on Multiple Input Multiple Output Mode Diversity Coherent Reception

作　　者：尹涵 宋英雄 李迎春[1,2] 陈松 黄烨恬[1,2] Yin Han;Song Yingxiong;Li Yingchun;Chen Song;Huang Yetian(Key Laboratory of Special Optical Fiber and Optical Access Network,School of Communication and Information Engineering,Shanghai University,Shanghai 200444,China;International Research Laboratory of Specialty Fiber Optics and Ad vanced Communication,Shanghai University,Shanghai 200444,China)

机构地区：[1]上海大学通信与信息工程学院特种光纤与光接入网重点实验室,上海200444 [2]上海大学特种光纤与先进通信国际合作联合实验室,上海200444

出　　处：《中国激光》2022年第23期123-131,共9页Chinese Journal of Lasers

基　　金：国家重点研发计划(2021YFB2900800);上海市科委项目(20511102400,20ZR1420900);高等学校学科创新引智计划(111)(D20031)。

摘　　要：针对自由空间光通信(FSO)系统中大气湍流导致大气信道折射率不稳定,进而对传输光信号造成损伤导致误码率升高等问题,本文提出了一种基于LP_(01)、LP_(11a)和LP_(11b)两模组光纤的少模分集接收结合相干检测信号处理的方案,以对抗FSO系统中大气湍流对系统性能的影响,从而提高接收机的性能。根据Gamma-Gamma(G-G)大气湍流信道模型,采用基于时频域最小均方(LMS)的多入多出(MIMO)信号处理算法,通过VPI仿真软件模拟光场在弱、中、强三种强度大气湍流(弱、中、强大气湍流下,折射率结构参数C_(n)^(2)的取值分别为2.1×10^(-16)、3.51×10^(-14),2.6×10^(-13))条件下的传输,进行传输速率为100 Gbit/s的偏振复用正交相移键控(DP-QPSK)自由空间光传输仿真实验。实验结果表明,相比于单模光纤接收,采用三模光纤接收可在弱、中、强三种湍流强度下使接收性能分别提高1.8 dB、2.5 dB和3 dB。Objective Free-space optical communication has a high communication rate,large capacity,good confidentiality,small size,light weight,low power consumption,and strong anti-interference ability.An instantaneous deployment or setup of a mobile platform communication system is possible.The invention of high-power light sources overcomes the issue of optical signal attenuation in mild weather.Atmospheric turbulence can result in beam drift,beam expansion,light intensity flicker,angle of arrival fluctuation,and other influences,especially at a distance of 1 km or more,which will increase the bit error rate of the link,degrading the communication performance.For an free-space optical communication system,adaptive optical compensation,coherent reception,mode diversity reception,and other technologies have been studied to reduce the impact of atmospheric turbulence.More optical signals can be coupled into the fiber as unrelated signals,and the orthogonality of the mode can conduct diversity reception using multiaperture and multimode fiber for signal acquisition.In this study,we first introduce the turbulent atmospheric channel and the Gamma-Gamma model.We derive the electric field distribution,coupling efficiency,and normalized cutoff frequency of the few-mode fiber receiving under weak conductance.Second,we establish the simulation system of 100 Gbit/s DP-QPSK free-space optical transmission with mode diversity reception and use the LMS-MIMO(multiple input multiple output based on least mean square)equalization algorithm for digital processing.We hope that our experimental results can be helpful for the study of using mode diversity receiver technology in atmospheric turbulence.Methods In this study,an experimental system of 100 Gbit/s DP-QPSK free-space optical transmission with mode diversity was set up.First,the optical carrier passed through the atmospheric channel and was received using few-mode fiber.Using independent transmission of signals in different modes,the few-mode fiber could transmit more signals.Additio

关 键 词：光通信 大气湍流 Gamma-Gamma模型 少模光纤 多入多出 

分 类 号：TN929.12[电子电信—通信与信息系统]