Research On Atmospheric Turbulence Phase Screen Simulation Technology Based On Sparse Spectrum

In the study of atmospheric space optical communication,due to the influence of atmospheric turbulence,the system's bit error rate will increase when the beam is transmitted in the atmosphere,and the communication performance of the system will deteriorate.In order to improve the quality of space optical communication,it is necessary to find a method to suppress the effects of atmospheric turbulence.However,due to the high cost and low efficiency of external field tests,simulating atmospheric turbulence is a high-efficiency and low-cost technical method for the simulation test of the performance of space optical communication systems in the laboratory.We mostly uses numerical simulation methods based on classical turbulence theories such as Kolomogrov and Von Karman to simulate atmospheric turbulence.However,these models are complex in form and lack detailed information.The sparse spectrum turbulence theory has the characteristics of simple form and no period,which can describe more details of turbulence,and the mathematical partitioning method does not involve the transformation in the frequency domain.there is no periodicity problem and the transformation form is simple.Therefore,the turbulence numerical simulation,whose method based on the mathematical partitioning method of the sparse spectral turbulence theory,has a good application prospect.In this paper,the turbulence simulation technology based on the mathematical partition method of sparse spectrum model is studied.First,according to the characteristics of the phase function of the sparse spectrum turbulence model,the direction,size and amplitude of the light wave are analyzed mathematically,so that the phase screen obtained can meet the mathematical requirements of the phase structure function and phase function.Compared with the classical phase screen simulation method,the calculation of the mathematical partition method is significantly smaller.Under the atmospheric coherence lengths of 0.01 m,0.05 m,and 0.1m,the grayscale image of phase screen which generated by the logarithmic partition method and the power spectrum inversion method are compared,and the phase structures are generated separately.The comparison chart of function curves shows that the details of the partition model are richer,and the fitting degree of the structure function curve is higher according to the turbulence density.Then,the obtained phase screen is continuously loaded on a Liquid Crystal On Spatial Light Modulator(LC-SLM),and collect light spot information of different atmospheric vapor dry lengths.Based on the spot information collected by the camera,parameters such as the spot radius,beam arrival angle,and beam drift were calculated to verify the match with the real atmospheric turbulence effect.It is verified that the shorter the atmospheric coherence length is,the stronger the turbulence disturbance is,which in line with the law of atmospheric turbulence disturbance.the verification index of the atmospheric turbulence effect is whin the normal range.Finally,based on the calculation of the turbulence effect,the atmospheric refractive index constant and the atmospheric coherence length were verified.The characteristic parameters of these two atmospheric turbulences are also within the normal range of the corresponding turbulence intensity.The simulation and experimental test results show that the sparse spectrum partitioning method has the advantages of simple operation,long simulation period,etc.,and can better simulate real atmospheric turbulence.In summary,the research done in this paper provides a simulation method for sparse spectrum atmospheric turbulence simulation and provides a reference for optimizing space optical communication systems.