Orbital angular momentum (OAM) has aroused widespread interest in communication systems because it improves spectrum efficiency. However, for the free-space link, OAM-based communications encounter problems of OAM beam divergence and misalignment, which reduces the channel quality. To address these two challenges, we propose an algorithm to detect the OAM beams based on the dynamic mode decomposition (DMD). Only the partial receiving aperture is used to address the challenge caused by the beam divergence, and the output DMD spectrum exactly sorts the OAM indices of superposed modes. Besides, when there is a misalignment, the DMD spectrum is utilized as a feedback indicator to search for the lateral displacement of the mode axis. With the differential evolution, the axis of OAM beams can be located. Compared with existing detection schemes, our work enables the separation of mixed OAM modes with less received information, and the perfect alignment is dispensable as a priori. This decentralized partial aperture receiving scheme could serve as a practical and effective detection technique for OAM-based communication systems.

轨道角动量（OAM）因其提高了频谱效率而引起了通信系统的广泛兴趣。然而，对于自由空间链路，基于OAM的通信会遇到OAM波束发散和未对准的问题，从而降低了信道质量。为了解决这两个挑战，我们提出了一种基于动态模式分解 (DMD) 检测 OAM 光束的算法。仅使用部分接收孔径来解决光束发散带来的挑战，输出 DMD 光谱准确地对叠加模式的 OAM 指数进行排序。此外，当存在未对准时，利用 DMD 谱作为反馈指标来搜索模式轴的横向位移。通过差分演化，可以定位OAM光束的轴。与现有检测方案相比，先验的。这种分散的部分孔径接收方案可以作为基于 OAM 的通信系统的实用和有效的检测技术。