为了研究雪崩光电二极管(APD)对大气传输后的激光进行探测时, 所受大气湍流效应及APD噪声的影响, 分析了激光在湍流大气中传输、APD对激光探测两个过程, 结合APD的探测原理, 建立了指数威布尔-高斯双重随机过程模型。通过实验测量了不同信噪比、不同大气湍流下APD输出电流的概率密度, 对探测距离不同、接收口径不同的情况进行了仿真。结果表明, 接收信噪比为2,5,10时, 光强分布方差分别为0.5354,0.3565,0.2781, 偏移量分别为0.05,0.0109,0.0029; 大气折射率结构常数为2.5×10-15,3×10-14,4.9×10-14时, 方差分别为0.1198,0.2781,0.4035, 偏移量分别为0.0002,0.0029,0.0039; 双重随机过程模型可准确描述经过大气传输的激光被APD探测的过程; 探测器口径的变化对APD输出电流的概率密度影响不大, 而接收信噪比、探测距离、大气折射率结构常数的增大会使APD输出电流平均值较信号电流产生较大偏移、且离散程度加剧。该模型的建立对激光探测技术研究具有一定的参考价值。

In order to study effect of atmospheric turbulence and avalanche photodiode (APD) noise when an APD receiving laser transmitted in turbulent atmosphere, both processes, i.e., laser propagation in turbulent atmosphere and laser detection by APD were analyzed. Then, combined with the detection principle of APD, the exponential Weibull-Gauss dual stochastic process model was established. The probability density of APD output current under different signal-to-noise ratios and atmospheric turbulence was measured. Different detection distances and receiving apertures were simulated. The results show that, when the received signal-to-noise ratio is 2, 5 and 10, the variances of light intensity distribution are 0.5354, 0.3565 and 0.2781, respectively and the offsets are 0.05, 0.0109 and 0.0029, respectively. When the structure constants of atmospheric refractive index are 2.5×10-15,3×10-14,4.9×10-14, the variances are 0.1198, 0.2781 and 0.4035, respectively and the offsets are 0.0002, 0.0029 and 0.0039, respectively. The dual stochastic process model can accurately describe the process for APD detecting laser transmitting in turbulent atmosphere. The change of detector aperture has little effect on the probability density of APD output current. With the increase of the received signal-to-noise ratio, detection distance and atmospheric refractive index structure constant, the average output current of APD is larger than that of signal current. And the degree of dispersion is aggravated. The establishment of this model has a certain reference value for the research of laser detection technology.