大气湍流对光偏振度的影响

Effect of the Turbulent Atmosphere on DOP of Light Beams

偏振调制激光通信系统采用偏振光携带信息,可以降低背景光噪声,提高信噪比,大幅提升系统性能。但是,由于受到大气湍流效应的影响,激光的偏振特性会发生变化。所以研究大气湍流对光偏振特性的影响对提高应用偏振信息的大气激光通信系统性能具有重要意义。论文通过理论分析并借助Matlab软件进行模拟仿真,研究大气湍流对各种状态的偏振光偏振度的影响。结果表明激光在大气湍流环境中,只要传输距离足够远,最终都会恢复到初始偏振度值;且要保证激光在传输过程中保持偏振特性不改变,就要求激光满足以下条件之一:1)线偏振光;2)满足δxx=δyy且Bxy=0条件的部分偏振光;3)满足δxx=δyy=δxy条件的任意偏振光。

The polarized light applied in the atmosphere optical communication system with polarization modulation carrying information is in order to increase the signal to noise ratio and reduce the background light noise as well for effectively improving the property of this system. But it is influenced by the atmosphere turbulence,and the polarization character of the laser signal changes.So it is of great importance to focus on the research of the influence on polarization character of the laser beam caused by the atmospheric turbulence. This research is significantly meaningful to improve the property of atmosphere optical communication system. In this thesis,the theory analysis is applied in the study of effects on the degree of polarization(DOP)of the laser signal with all polarized state in turbulence and the software of Matlab is used to simulate this influence. It is testified that the DOP will finally get stable when the distance is long enough. For keeping polarization stabilized to transmit in turbulence,the laser must be content with one of these demands:1)The linearly polarized light. 2)The part polarized light with δxx= δyy and Bxy= 0. 3)Any polarized state light with δxx= δyy= δxy.