| Atmospheric laser communication is a new communication mode,which has a series of advantages such as wide communication frequency band,large information capacity,fast transmission rate,strong anti-interference,strong anti-interception ability and high confidentiality.However,atmospheric turbulence has a serious effect on atmospheric laser communication,and the scintillation effect of atmospheric turbulence will seriously affect the communication quality of atmospheric laser communication system.Therefore,suppressing the scintillation effect caused by atmospheric turbulence and improving the communication quality of atmospheric laser communication system have become one of the main problems to be solved at present.To suppress the scintillation effect,scholars at home and abroad have proposed diversity technology,high power emission,large aperture receiving technology,adaptive optical compensation technology and other technologies to suppress the scintillation effect of atmospheric turbulence.In this paper,the scintillation effect under complex urban path is analyzed,and the inhibition effect of diversity technology and large aperture receiving technology on atmospheric turbulence scintillation effect is analyzed.For atmospheric laser communication system under complex horizontal city path,the composition of atmospheric channel is relatively complex,and the temperature gradient in the atmospheric channel changes greatly,so the influence of atmospheric turbulence on the communication system is very serious.In this paper,the atmospheric turbulence under the experimental link is monitored,and the relationship between the structure constant of atmospheric refractive index and scintillation index in the atmospheric channel and the variation trend of the two indexes throughout the day are analyzed.By comparing the theoretical distribution curve of the normalized light intensity probability density function with the actual monitoring data,it is concluded that when the scintillation index is less than0.35,the distribution curve of the probability density function tends to be normal.When the scintillation index is greater than 0.35,the probability density function distribution curve tends to a negative exponential distribution,and the turbulence intensity gradually tends to strong turbulence.Diversity transmission and diversity reception in diversity technology have a suppressive effect on atmospheric turbulence.In this paper,the suppression effect of different numbers of transmitting antennas and receiving antennas is analyzed,and it is concluded that when the distance between the transmitting antenna and the receiving antenna is greater than the coherence length.As the number of transmitting antennas and receiving antennas increases,the scintillation index decreases accordingly.Therefore,diversity technology can suppress the scintillation effect of atmospheric turbulence to a certain extent and improve the communication quality of the communication system.Under the same experimental link and experimental conditions,the large-aperture receiving technology also has a good suppression effect on the atmospheric turbulence scintillation effect.In this paper,the large-aperture Cassegrain receiving system is used to monitor the all-sky scintillation index,and it is verified at the same time.The scintillation index is analyzed for different receiving apertures,and it is concluded that as the receiving aperture increases,the flicker index decreases significantly,and the communication quality of the communication system is significantly improved.Therefore,increasing the receiving aperture can effectively suppress the atmospheric turbulence scintillation effect.Through the analysis of the inhibition effect of diversity technology and large aperture receiving technology on the atmospheric turbulence scintillation effect,the communication quality of the communication system can be effectively improved,which provides a reference for the suppression of atmospheric turbulence in the free space laser communication system. |
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