Research On Diversity Technology In Atmospheric Partially Coherent Optical Communication

Free space optical communication takes laser as carrier,which has the advantages of high bandwidth,good security,easy installation,low cost and anti electromagnetic interference.It is widely used in satellite ground communication,military security,temporary link construction and other scenes.However,laser propagation in the atmosphere will be affected by turbulence,resulting in the effects of light intensity flicker,beam drift,spread,wavefront distortion and so on,which will reduce the performance of free space optical communication system.Therefore,how to overcome the influence of atmospheric turbulence and improve the reliability of free space optical communication is always the core problem of free space optical communication.This paper focuses on the atmospheric transmission technology of partially coherent light,summarizes the research status of free space optical communication at home and abroad,analyzes the physical mechanism of atmospheric channel including atmospheric attenuation and atmospheric turbulence on laser transmission,expounds several methods to suppress atmospheric turbulence effect,and analyzes their respective advantages and disadvantages.Aiming at the complex turbulent environment,the diversity receiving technology of space optical communication based on partially coherent light is studied.The spatial diversity technology is mainly discussed.The phase screen is used to simulate atmospheric turbulence.The signal-to-noise ratio(SNR)variation characteristics of free space optical communication under different diversity multiplicities are simulated.The bit error rate(BER)characteristics of communication system are studied and analyzed with Rytov exponent as a parameter,The relationship between diversity multiplicity and atmospheric channel characteristics in complex turbulent environment is obtained.On this basis,using the turbulent atmosphere experimental simulation device,using the partially coherent Bessel Gaussian ring beam,combined with the characteristics of the partially coherent beam,the optical transmitting and receiving circuits are designed and developed,and the experimental system of partially coherent optical communication is built.The SNR of coherent and partially coherent beams in different turbulent environments and the optical receiving performance with different diversity multiplicity are measured and compared.The experimental and analytical results show that the anti turbulence ability of partially coherent optical communication system is better than that of fully coherent optical communication system;In the complex turbulent environment,the signal-to-noise ratio of the communication system can be increased by more than 3d B by using spatial diversity reception,and the performance of the communication system can be significantly improved.