Research On Channel On Noise In Wireless Optical Coherence Communication And Its Effect On Coherence Detection Performance

Free Space Optical Communication(FSO)is a kind of communication method that transmits information in free space with laser signal as the communication carrier.Compared with traditional communication methods,free space optical communication has the advantages of wide spectrum,strong confidentiality,good anti-interference ability and low power consumption.Therefore,free space optical communication has good application potential in interastral,satellite-ground and terrestrial applications.As current mainstream communication technology,coherent optical communication is compared with the traditional IM/DD direct detection system.By using this technology,light field information with rich phase,frequency and amplitude can be detected.Therefore,atmospheric coherent optical communication system using high order modulation technology,coherent detection technology and digital signal processing technology has become a hot topic in the field of optical communication.In this article,main work finished is as follows:1.A new coherent optical detection system is designed and the signal of signal light is amplified by the local oscillation signal to improve the detection sensitivity.A wireless coherent laser communication model is established and the system working principle is discussed in detail and the simuiation experiment is carried out for verification,which lays a theoretical foundation for the implementation of this method.2.For the designed coherent optical communication system,the working principle of dual-balanced detection system is deduced by mathematics.The balanced mismatch is analyzed and discussed from the two aspects of optical mixer and balance detector of the dual-balanced detection system.The signal-to-noise ratio formula of coherent detection system with common-mode rejection ratio is derived and effects of thermal noise,relative strength noise and common-mode rejection ratio on system performance are analyzed in detail3.The optical statistical characteristics of atmospheric turbulence and its impact mechanism on transmission of optical beam are summarized.According to the principle of coherent detection,expressions of Ber and SNR(signal-to-noise ratio)of atmospheric coherent optical detection communication system are derived.Based on Kolmogorov turbulence theory,the numerical analysis of atmospheric laser signal transmission in turbulent flow is carried out and the signal-to-noise ratio(SNR)analytical expressions of coherent optical detection system under the influence of strong scintillation are analyzed4.The paper establishes a formula for impact of the relationship between wavefront distortion and wave length of signal light on error rate,and studies the channel noise in wireless optical coherent communication and its impact on coherent detection performanceWith the rapid development of free space optical communication technology,new theories are needed as the basis.The research work of this paper solves the basic scientific problem that needs to be solved urgently in coherent optical communication,the problem of the influence of atmospheric channel on laser link and the analysis of the influencing factors of coherent detection.This study provides an important theoretical basis for the development of key technologies such as targeting,tracking,capture and communication in wireless coherent communication systems,and also lays a foundation for the optimization of communication systems.