大气湍流中超短高斯激光脉冲的时间域展宽模型研究

穿过大气湍流的高斯激光脉冲在时间域的展宽行为与高斯脉冲通过理想高斯滤波器后的时域展宽行为相似。因此,为了激光通信信道仿真的需要,提出用级联巴特沃斯滤波器来逼近理想高斯滤波器的方法对这种时间域上的展宽行为进行建模。逼近后的高斯滤波器的3dB频率点与大气湍流的物理参数(包括折射率结构常数和湍流外尺度)和传播几何路径长度联系在一起,从而将高斯脉冲的展宽与所通过的大气湍流环境参数相结合并得到了模拟高斯脉冲展宽的解析表达式。该模型和由模型参数表示的高斯脉冲展宽的解析表达式不仅在湍流弱起伏区有效,而且在从弱起伏到中等起伏再到强起伏的整个区域中都有效。

Study of Time-Domain Spreading Model of Ultrashort Gaussian Laser Pulses in Atmospheric Turbulence

The temporal spreading behavior of Gaussian laser pulses propagating through atmospheric turbulence is similar to the behavior of Gaussian pulses passing through Gaussian filter. Hence, a temporal spreading model, being a Gaussian filter approximated by cascading Butterworth filters in essence, is proposed for laser communication channel simulation. The 3 dB frequency point of the approximated Gaussian filter is closely associated with the physical parameters of atmospheric turbulence, including the structural constant of refractive index as well as the outer scale size of turbulence, and propagation path length. So the spreading of the Gaussian pulses is combined with the parameters of atmospheric turbulence, and an analytic expression for modeling the spreading is obtained. This model and the analytic expression represented by the model′s parameters are not only valid in weak fluctuation regime but also in weak-moderate-strong regime.