The Effects Of Atmospheric Channel On Wireless-laser Communication

The atmospheric laser communication is free-space optical communication' specific implementation on earth. It is primarily feathered by flexible access method and low cost in short distance and can acquire the same capacity as fiber transmission. It is easy to be designed, is convenient to be switched-on, has high-speed and low-cost, so it is one of the most effective schemes to settle the problem of "The Last One Kilometer" and has been widely applied in such fields as intelligence building and military.In systems of atmospheric laser communication, because effects of atmospheric scattering, interception, turbulence and other factors, during the course of transmission, laser signals' energy attenuation, light intensity flashing, light beam' random inflection. Whether we can overcome these effects is the key of atmospheric laser communication' population, so it is extremely important to research atmospheric laser communication channel. The main contents of this paper are:Firstly, this paper introduces characters of atmospheric laser communication and existing condition at home and abroad. Analyses its principle and key technologies and the subject studied future. Secondly, Based on the analysis of atmosphere channel, we analysis the atmospheric absorbing, scattering and turbulent. Atmospheric absorbing and scattering cause the attenuation of light energy. Atmospheric turbulent cause the flashing of the light intensity and so on.Thirdly, we explore the atmospheric attenuation, because the atmospheric attenuation that atmospheric absorbing and atmospheric molecule scattering cause can be ignored. We study the effects of atmospheric decay, scattering and turbulence on laser communication. Emulates atmospheric decay, finds the results is different greatly with theoretical value, and the deviation becomes greater with wavelength' increase, after analyzing gets the conclusion the results has relation with q. Fits and amendments q, analogues atmospheric decay with the new q, finds the correct q.In the end, Based on atmospheric turbulence' Maxwell equation and characters, get Maxwell equation of light intensity fluctuation in atmospheric turbulence and distribution of light intensity on receiving area. Through analysis cumulative probability and statistical regularity of the light intensity fluctuation. Finds increase the receiving surface elements can decrease the variance of the light intensity fluctuation. Further we study the quantity of apertures sending can reduce the variance of the light intensity fluctuation. In the end, we analysis the BER that be caused by single aperture and quantity of apertures. The conclusion shows that n apertures and long wavelength can reduce the BER.