发表机构
Beijing University of Posts and Telecommunications; State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications; Science and Technology on Space Physics Laboratory; Xiong’an Aerospace Information Research Institute; Beijing Institute of Technology; School of Optics and Photonics, Beijing Institute of Technology（北京邮电大学; 北京邮电大学网络与交换技术国家重点实验室; 空间物理科学与技术实验室; 雄安航天信息研究院; 北京理工大学; 北京理工大学光学与光子学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究针对OAM复用FSO通信，推导了湍流通道中涡旋光束的接收面辐照度、解复用端口功率等统计特性，评估了SER，发现小接收孔径下复用性能对模态间距更敏感。
AI 中文摘要
轨道角动量（OAM）复用可提升自由空间光（FSO）通信的容量，而大气湍流会引发模态串扰与辐照度波动，劣化解复用性能。因此，分析建模对表征湍流引发的传播效应及OAM通道的解复用端口功率统计特性至关重要。本文首先研究涡旋光束经湍流通道传播后的接收面辐照度统计特性，利用频域卷积推导平均辐照度，并基于扩展Rytov理论得到闭式频域衍射核，以评估中等与强湍流下的闪烁指数。但仅接收面辐照度统计不足以描述OAM复用FSO通信的性能，故进一步推导解复用端口功率统计特性，具体而言，基于一般拉盖尔-高斯（LG）涡旋场的复高斯展开与扩展惠更斯-菲涅耳框架，推导平均端口功率、模态串扰、端口功率方差及跨端口协方差，随后利用解复用端口功率统计评估OAM复用FSO通信的符号差错率（SER）。数值结果表明，所有推导的统计特性与不同湍流强度及光束参数下相位屏仿真所得结果一致；所得SER性能进一步显示，相较于大接收孔径，小接收孔径下OAM复用性能对模态间距更敏感。
英文摘要
Orbital angular momentum (OAM) multiplexing can increase the capacity of free-space optical (FSO) communications, whereas atmospheric turbulence causes modal crosstalk and irradiance fluctuations that degrade demultiplexing performance. Analytical modeling is therefore important for characterizing turbulence-induced propagation effects and the demultiplexed port-power statistics of OAM channels. In this paper, we first study the receiver-plane irradiance statistics of vortex beams after propagating through the turbulent channel. The average irradiance is derived using frequency-domain convolution, and a closed-form frequency-domain diffraction kernel is obtained based on extended Rytov theory to evaluate the scintillation index for moderate and strong turbulence. However, receiver-plane irradiance statistics alone are insufficient to describe the performance of OAM-multiplexed FSO communications. We therefore derive the demultiplexed port-power statistics. Specifically, we derive the average port power, modal crosstalk, port-power variance, and cross-port covariance based on the complex Gaussian expansion of general LG vortex fields and the extended Huygens-Fresnel framework. The demultiplexed port-power statistics are then used to evaluate the symbol-error rate (SER) of OAM-multiplexed FSO communications. Numerical results demonstrate that all derived statistics are consistent with those obtained by phase-screen simulations under different turbulence strengths and beam parameters. The resulting SER performance further shows that OAM-multiplexing performance is more sensitive to mode spacing for small receiver apertures than for large apertures.
Comments10 figures; submitted to IEEE Journal of Lightwave Technology; currently under peer review
