相位屏法仿真海洋湍流激光传输特性有效性

Validity of beam propagation characteristics through oceanic turbulence simulated by phase screen method

海洋湍流是制约水下激光通信应用的重要因素之一,相对于大气湍流,海洋湍流在较短距离内即可达到强起伏,针对强湍流传输特性及数值仿真的可靠性验证具有重要意义。基于大气湍流传输特性理论公式,利用大气湍流参数等效表达海洋湍流的方法给出了弱起伏到强起伏条件下海洋湍流传输特性的理论计算公式。针对相位屏法在海洋湍流仿真中的应用,给出了选取相位屏间距、网格尺寸和网格数目的基本要求,并数值仿真了海洋湍流不同参数条件下的传输特性,与理论计算结果进行了对比。结果表明:基于相位屏法得到的光强一阶矩传输特性参量与解析结果较为一致,但是在强闪烁条件下数值仿真光强闪烁特性与理论结果偏差较大。

Oceanic turbulence is an important factor to restrict the application of underwater optical communication.Phase screen method is a simple and effective way to simulate the propagation process of complex beams through turbulence.The constraints of parameter setting for phase screen simulated oceanic turbulence based on the sampling principle and turbulence effects were firstly discussed here.Furthermore,the theoretical expressions of propagation characteristics of Gaussian beam through oceanic turbulence from weak to strong fluctuation regime were derived.Our goal in this research was to testify the validity of phase screen method in oceanic turbulence by comparison of major statistical characteristics of Gaussian beam propagating in oceanic turbulence simulated by phase screen method and the theoretical expressions derived.Results show good match between simulation results and theory formulas for long exposure beam radius and centroid displacement under different turbulence conditions,as well as the scintillation index under weak fluctuation regime.However,results show significant mismatch between numerically estimated and theoretically predicted values for the onaxis scintillation index in strong fluctuation regime.