Study On Atmospheric Turbulence Characteristics And Optimization Of Near-Earth Space Laser Communication Link

Atmospheric laser communication is an emerging communication method,which has many advantages such as wide bandwidth,large information capacity,fast transmission rate,strong anti-interference and anti-interception capabilities,as well as high confidentiality.However,atmospheric turbulence in the transmission medium can seriously affect atmospheric laser communication,especially the scintillation effect of the signal,which greatly reduces the communication quality.Currently,the research focus in the field of space laser communication is to explore the characteristics of atmospheric turbulence and study how to suppress its impact on atmospheric laser communication.This article investigates atmospheric laser communication in urban link environments,but due to the complexity of the atmospheric channel,this communication method is affected by many factors.One of the most serious problems is atmospheric turbulence.In addition,the composition of the atmosphere is also very complex,and the temperature gradient changes greatly,which also has an impact on communication.Research based on atmospheric turbulence characteristics indicates that,compared with other common statistical models,the Gamma-Gamma distribution model and the exponential Weibull distribution model have a wider range of applications and perform better in handling details,making them more suitable for theoretical derivation and simulation.However,when the turbulence intensity weakens to a certain degree,the Gamma-Gamma distribution model is no longer applicable,while the fitting degree of the exponential Weibull distribution model remains high.However,the computation of the exponential Weibull distribution model is the most complex among several commonly used distribution models.In addition,in strong turbulence environments,the negative exponential distribution model has better fitting effect,while in weak turbulence environments,the fitting effect of the exponential Weibull distribution model and the log-normal distribution model are better.Compared with the exponential Weibull distribution model,although the negative exponential distribution model and the log-normal distribution model have simpler calculations,their application range is small.Therefore,in different situations,it is necessary to choose the appropriate distribution model based on its advantages.This article analyzes spatial diversity technology and large-aperture receiving technology and draws conclusions through experiments.With the increase of the number of transmitting apertures or the area of receiving apertures,the scintillation index and bit error rate will both decrease.Under the premise of weak turbulence environment and controlling the same receiving aperture area,using a three-aperture transmission system can achieve a bit error rate gain of more than one order of magnitude compared to a single-aperture transmission system.Similarly,controlling the same number of transmitting apertures,using a 90 mm receiving aperture can also achieve a bit error rate gain of more than one order of magnitude compared to a 45 mm receiving aperture.Therefore,these two technologies can improve the communication quality of the laser communication system to a certain extent.