兰州地区光强分布及其起伏特性研究

在兰州地区夜间进行了链路长为610m的激光传输实验,研究了高斯激光在不同天气条件下的光强分布及其起伏特性.采用三维伪彩色变换方法,分析了光斑光强的空间分布规律,得到了光斑主瓣光强服从类高斯分布,并按照晴天、多云天、阴天的顺序,光斑几何中心位置附近光强分布的陡峭度依次减小,而其衰减则依次增大的结论.同时,利用实测光强值分析了大气闪烁指数,结果表明:晴天、雨后晴天和阴天下的闪烁指数分别为0.225 4、0.189 2、0.188 8,这说明晴天下的光强起伏大于雨后晴天和阴天的,且均为弱起伏.通过对归一化光强的频数分布进行非线性拟合得到了光强的概率密度分布,它们均服从对数正态分布,其中晴天下的概率密度曲线的拟合优度更是达到了0.997 50.

Experimental Investigation of Light Intensity Distribution and Fluctuation Characteristics in Lanzhou Area

A wireless optical link in length of 610 m is established in Lanzhou area to investigate the light intensity distribution and fluctuation characteristics of Gaussian laser under different weather conditions.The three-dimensional pseudo-color transform method is utilized to analyze the spatial distribution of light intensity.The results show that the intensity distribution of the main lobe within the light spot follows the Gaussian distribution.The steepness of light intensity distribution decreases and the attenuation of light intensity increases according to the order of sunny day, cloudy day and overcast day in turn.Moreover, the atmospheric scintillation index is analyzed by using the measured light intensity data.The results show scintillation index of sunny day, sunny day after rain and overcast day are 0.225 4, 0.189 2 and 0.188 8, respectively.This indicates that the light intensity fluctuation in sunny day is higher than sunny day after rain and overcast day.The probability density distribution of light intensity is obtained by using nonlinear fitting of histograms of the normalized optical intensity data.They all conform to log-normal distribution.Especially, the probability density in sunny day is more consistent with log-normal distribution, the goodness of its fitted curve is up to 0.997 50.