State Key Lab of Applied Optics, Changhun Institute of Applied Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, Jilin, China.
Chinese Academy of Sciences University, Beijing, China.
Sci Rep. 2018 Jan 18;8(1):1124. doi: 10.1038/s41598-018-19559-9.
The performance of free-space optics communication (FSOC) is greatly degraded by atmospheric turbulence. Adaptive optics (AO) is an effective method for attenuating the influence. In this paper, the influence of the spatial and temporal characteristics of turbulence on the performance of AO in a FSOC system is investigated. Based on the Greenwood frequency (GF) and the ratio of receiver aperture diameter to atmospheric coherent length (D/r ), the relationship between FSOC performance (CE) and AO parameters (corrected Zernike modes number and bandwidth) is derived for the first time. Then, simulations and experiments are conducted to analyze the influence of AO parameters on FSOC performance under different GF and D/r . The simulation and experimental results show that, for common turbulence conditions, the number of corrected Zernike modes can be fixed at 35 and the bandwidth of the AO system should be larger than the GF. Measurements of the bit error rate (BER) for moderate turbulence conditions (D/r = 10, f = 60 Hz) show that when the bandwidth is two times that of GF, the average BER is decreased by two orders of magnitude compared with f /f = 1. These results and conclusions can provide important guidance in the design of an AO system for FSOC.
自由空间光通信（FSOC）的性能会受到大气湍流的严重影响。自适应光学（AO）是一种衰减这种影响的有效方法。本文研究了湍流的时空特性对 FSOC 系统中 AO 性能的影响。基于格林伍德频率（GF）和接收器孔径直径与大气相干长度的比值（D/r），首次推导出 FSOC 性能（CE）与 AO 参数（校正泽尼克模式数量和带宽）之间的关系。然后，进行了仿真和实验，以分析在不同 GF 和 D/r 下 AO 参数对 FSOC 性能的影响。仿真和实验结果表明，对于常见的湍流条件，可以将校正泽尼克模式的数量固定在 35，并且 AO 系统的带宽应大于 GF。对中等湍流条件（D/r = 10，f = 60 Hz）的误码率（BER）测量表明，当带宽是 GF 的两倍时，与 f / f = 1 相比，平均 BER 降低了两个数量级。这些结果和结论可以为 FSOC 的 AO 系统设计提供重要指导。
