Abstract Due to the complexity and strong fluctuations of atmosphere turbulence, it is always a challenging task to mitigate atmospheric turbulence effects in space optical communications. In this paper, we demonstrate a shared local oscillator (LO) spatial diversity polarization multiplexing coherent optical orthogonal frequency division multiplexing (PM-CO-OFDM) system based on group timing synchronization and diversity branch phase correction in downstream low earth orbit satellite-to-ground (LEO-StG) optical communications. For the shared LO coherent receiver system, the maximal ratio combining (MRC) technique is used at the receiver to improve the system performance, and the diversity gain is found to depend on the relative phase offset (RPO) among the different branches. Simulation results under different turbulence channels not only demonstrate that the RPO can be effectively compensated by group timing synchronization and diversity branch phase correction, but also show the improvement in receiver sensitivity. Furthermore, the number of optimal branches is also investigated. The superiorities of such spatial diversity scheme make it highly desirable for potential application in LEO-StG optical communications.

中文翻译：

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星地光通信中基于群定时同步和分集分支相位校正的共享本振空间分集PM-CO-OFDM系统

摘要 由于大气湍流的复杂性和强波动性，在空间光通信中减轻大气湍流效应一直是一项具有挑战性的任务。在本文中，我们展示了一种基于群定时同步和分集分支相位校正的共享本地振荡器（LO）空间分集极化复用相干光正交频分复用（PM-CO-OFDM）系统，用于下游低地球轨道卫星到地面（LEO-StG）光通信。对于共享LO相干接收系统，在接收端采用最大比合并（MRC）技术来提高系统性能，并且发现分集增益取决于不同分支之间的相对相位偏移（RPO）。不同湍流通道下的仿真结果不仅表明群时同步和分集支路相位校正可以有效补偿RPO，而且表明接收机灵敏度有所提高。此外，还研究了最佳分支的数量。这种空间分集方案的优势使其在 LEO-StG 光通信中的潜在应用非常理想。