Study Of The Characteristic Of Beam Wander And Spreading In The Atmosphere Turbulence

The transmission of Light in atmosphere is affected by atmospheric turbulencewhich generates a series of turbulence effects, such as: intensity scintillation, beamspreading, beam wander and spot shake, and these effects influence the transmission ofoptical signals, especially the transmission of optical signals can be interrupted bybeam wander. This paper presents the analysis of beam wander and spreading causedby atmospheric turbulence.First of all, the power spectrums are introduced with considerations of differentfactors, as well as the light intensity of Gauss beam at any point in free space. Basedon the basic transmission theory in free space and the modified Andrews spectrums,the average intensity in weak turbulence is deduced applying the methods of Bornapproximation and Rytov approximation. Meanwhile, the high order and the averageintensity in strong turbulence are also derived utilizing the Markov approximation.Secondly, the characteristics of Gauss beam wander and spreading for the lightline of sight path propagation is studied. The long beam spreading of weak/strongturbulence is presented according to the calculation results of average light intensity ofweak/strong turbulence, as well as the numerical comparison with existed beamspreading results. The wander variance expression under different power spectrum arededuced using average intensity and different refractive index power spectrum, thenumerical results of beam wander is compared with the experiment data, the influenceof different weather and beam on the beam wander and spreading employing themodified Andrews spectrums are analyzed with considerations of the effect of the outerscale of atmospheric turbulence and the multiple scattering during the transmissionprocess.Finally, according to the horizontal transmission theory, the beam wander andspreading expression of slant transmission is presented.