Research Of Horizontal Atmospheric Layer Influnce On Laser Linear Polarization Properties

Recently the free space optical communication system attracts more attentionbecause of its high data transmission efficiency, excellent security, and portablewith high mobility. The polarized light is applied in the free space opticalcommunication in order to improve the signal to noise ratio and reduce thebackground light noise as well. The polarization division multiplexing can berealized and the efficiency of data communication can be improved by takingadvantage of orthogonal polarized light. When the laser signal transmits in thehorizontal atmosphere link, the polarization character will be influenced byatmosphere scattering and turbulence. It is of great importance to focus on theresearch of influence on polarization character of beacon light or signal lightcaused by atmosphere. This research is significantly meaningful to improve theproperty of free space optical communication system and even the satellite-groundoptical communication system.In this thesis, the influence on the polarization character of beacon light orsignal light in the link caused by the horizontal atmosphere communicationchannel. The Monte Carlo simulation is applied in the study of effects on laserlinear polarization character induced by atmosphere scattering and turbulencerespectively. Outfield experiments of horizontal atmosphere link are also taken out.Researches are done in this thesis by the following aspects:First of all, on the basis of Mie scattering theory, a Monte Carlo simulationwith the consideration of polarization character is designed and reasonablesimulation parameters are suggested. The polarized light scattering phase functionis deduced by taking the influence of water molecule and aerosol scattering on thepolarization character into account. The symmetric factor “g” in the H-G phasefunction is updated according to the scattering refractive index and scaleparameters simultaneously. The simulation is more close to the actual situationwith the help of this method. The polarization orientation as well as thepolarization state of different positions on the receiving plane is considered on thebasis of the former simulation. The distribution of polarization degree P of distinctpositions on receiving plane is discussed. In addition, the effects of variousreceiving aperture on polarization degree is also taking into account.Secondly, a Monte Carlo simulation with the consideration of polarizationcharacter is proposed and reasonable simulation parameters are suggested on thebasis of bubbles model of atmosphere and geometrical optics. The relationshipbetween atmosphere refractive index structure parameter Cn~2and atmosphere refractive index fluctuating standard deviation is analyzed. The effects ofhorizontal atmosphere link distance L as well as the atmosphere refractive indexstructure parameter Cn~2on the linear polarization character is deep analyzed.At last, the outfield experiments with the consideration of atmospherescattering and turbulence influence at the distance of11.16km are taken out. Theatmosphere refractive index structure parameter Cn~2is measured. There are twosets of experiment schemes are proposed in this part. The degree of transientpolarization P and the statistics power under different analyzer angles with a1/2wave plate are measured as well.This research has certain influence on the optimization of horizontalatmosphere link free-space optical communication system. In addition, it is thefoundation of application of polarization character on the satellite-ground opticalcommunication system.