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光束在大气湍流中传输时,大气湍流效应对光束进行强度和相位的随机调制,最终在远场处形成散斑。以部分相干高斯-谢尔模型(Gaussian-Schell Model,GSM)光束为研究对象,根据广义的HuygensFresnel原理、修正Von Karman谱模型,推导了GSM光束在大气湍流中传输时接收端光束的有效半径和平均散斑半径的表达式。利用数值计算对比分析光源相关参数和大气湍流对光束有效半径和平均散斑半径的影响。研究表明:光束的初始束腰半径越大、相干长度越小以及波长越小时,接收端光束的有效半径和平均散斑半径受湍流的影响越小;大气折射率结构常数越大,光束扩展越严重,此时平均散斑半径越小;光束有效半径和平均散斑半径随湍流外尺度增大几乎无变化,随湍流内尺度的增大而减小。所得出的结论对无线激光通信系统中光束的捕获、对准与跟踪(Acquisition,Pointing and Tracking,APT)系统的设计提供一个重要的参考价值。
When the light beam is transmitted in atmospheric turbulence, the atmospheric turbulence effects randomly modulate the intensity and phase of the light beam and eventually form speckles at the far field. Based on the generalized HuygensFresnel principle, the partially coherent Gaussian-Schell Model (GSM) beam is used as the research object. The Von Karman spectral model is modified and the effective radius of the beam at the receiver end when the GSM beam propagates in atmospheric turbulence is derived. The average speckle radius of the expression. The effects of light source parameters and atmospheric turbulence on the effective beam radius and the average speckle radius were compared and analyzed by numerical calculation. The results show that the larger the initial beam waist radius, the smaller the coherence length and the smaller the wavelength, the smaller the effective radius and the average speckle radius of the receiving end are affected by turbulence. The larger the atmospheric refractive index structure constant is, The mean speckle radius is smaller; the effective radius and the average speckle radius of the beam have almost no change with the increase of turbulence outer scale, and decrease with the increase of turbulence inner scale. The conclusions obtained provide an important reference value for the design of the acquisition, tracking and tracking (APT) system in the wireless laser communication system.