An Analysis Of Atmosphere Transmission Rate Of Laser Under The Fog And Haze Weather In FSO System

At present,the fog and haze weather becomes one quite harmful climate condition at most area of China.During the application of wireless light immunization system under this air condition,the fog and haze particles would cause the attenuation of laser,reduce the light signal of system receiver,hence decrease the property of BER performance in the system.In the extreme condition,it might result to"Off-target",which seriously impact the usage of wireless optical communication system,This essay mainly focuses on the scattering characteristics of particles and the penetration rate of laser under the fog and haze weather by modeling analysis.The receiving efficiency of laser at different communication distance would be evaluated in the air condition.This thesis analyzes the scattering characteristics for incidenl waves with different wavelength based con Mie Scattering Law using the simulation method for typical particles including fog particles,dust particles,bituminous coal particles,PM 2.5 particles and PM 10 particles in the Ifog and haze weather Besides,with the combining of the spectral distribution function and Mconte-Carlo method,the relationship in between of the density of particles and the maximum transmission distance of particles,transmission attenuation coefficien,transmission rate has been evaluated.The mcodelling illustrates that the extinction coefficient of particles increases with the scale parameters and finally approaches to 2,it is shown that the total energy attenuation caused by particles to laser is about twice as much as that caused by geometric crosssection energy attenuation..For different particles,the forward scatter is more obvious than backscatter,while the forward scattering dominates the general scattering.When the waive length of incident wave is high,the attenuation coefficient of later is relatively low,hence the corresponding maximum transmission distance of laser and the transmission rate would be high.The numerical values of laser propagation parameters at specific particle concentration are givenBased on the simulation,the link of 80m,340m and 2500m has been selected for the measurement of the power attenuation during the transmission of laser at the real haze weather condition.Referring to the definition connection and difference of fog environment and haze environment,the data which perfectly fits the fog environment and haze environment has been selected to draw the curve of system receiption power and the laser transmission that changes with the visibility.Finally,the basic principles of laser transmission in the fog and haze weather in Xi'an area have been derived.It could be concluded that all links of laser can be corresponded with specific empirical model during the transmission of laser in the smog weather based on the comparison of fog environment measuring curve and typical fog attenuation empirical model.It is demonstrated that the empirical model is worthy of reference for further researches at different visibility and transmission distance.