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光子轨道角动量(OAM)为光通信提供了新的高维自由度, 有望提高光信息传输系统信道容量, 解决当前通信资源紧张的问题. OAM键控(OAM-SK)是一种新型的信息传输机制, 其中, 对OAM模式的有效识别和检测是实现OAM-SK译码的核心技术之一. 本文提出了一种基于对数极坐标变换的OAM译码系统, 首先通过设计的坐标变换光栅进行映射, 再引入优化的相位校正光栅进行补偿, 最后采用一个傅里叶变换透镜实现了OAM模式的分离. 对系统在不同光栅参数下的分束效果进行数值评估, 在实验中成功实现了–35—+31阶轨道角动量模式的分束. 进一步地, 基于该OAM解复用系统, 搭建了自由空间光数据传输演示系统. 通过引入特定译码规则, 有效克服了对数极坐标变换存在的相邻模式混叠的问题, 实现了748934个码元的无误码传输. 本文结果为未来高容量光通信系统的发展提供了支持.Orbital angular momentum (OAM), as a novel high-dimensional degree of freedom, shows great potential applications in optical communication in improving system channel capacity and solving the problem of scarce communication resources. However, the effective recognition and detection of OAM modes are the core challenges for achieving efficient communication in such systems. In this work, an OAM decoding system consisting of a designed coordinate transformation device, a phase corrector, and a Fourier transform lens is presented based on log-polar coordinate transformation. The coordinate transformation device fabricated by liquid crystal polymer is utilized to map the incident vortex beam from polar coordinates into Cartesian coordinates, followed by the phase corrector to compensate for phase distortions into a collimated beam. Finally, the Fourier transform lens is used to separate the OAM modes at different space positions in its rear focal plane. The performance of the system is numerically evaluated in several ablation studies, and the influence of various grating parameters on beam separation efficiency is analyzed. Experimentally, the system successfully achieves the decoding of OAM modes ranging from –35 to +31 orders. Furthermore, a free-space optical communication demonstration system is constructed based on this OAM decoding system. By introducing specifically designed decoding rules, the system effectively mitigates the adjacent mode crosstalk inherent in logarithmic polar coordinate transformation and successfully transmitted 748934 symbols without errors. These favorable results highlight the capabilities of the proposed OAM-based optical communication system and provide valuable insights for developing future high-capacity optical communication networks.
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码元 0 1 2 3 4 5 6 7 OAM模式 — ±2 ±3 ±4 ±5 ±6 –6 –5 码元 8 9 A B C D E F OAM模式 –4 –3 –2 +2 +3 +4 +5 +6 
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