Research On Random Signal Detection Of Laser Communication In Atmosphere Turbulence Environment

With the development of laser technology,people pay more and more attention to the research of laser communication technology.Because of the turbulence effect in the atmosphere,the amplitude of the laser signal received at the receiver is eventually fluctuated,which will affect the accuracy of signal detection.In this dissertation,the detection method of random light intensity in atmospheric laser communication system under atmospheric turbulence channel is studied.First,this dissertation briefly introduces the development background and research status of signal detection technology of laser communication system in atmospheric turbulence in the environment,and the atmospheric laser communication link model were discussed,analysis of the formation of turbulence in the atmospheric laser,and the laser transmission power weakened.Followed by the comparison of several commonly used methods of detection of weak light signals,focuses on maximum likelihood sequence detection methods,application conditions and defects of it are analyzed.Then according to the noise characteristics and detection process of avalanche photodiode,the output signal model of receiver detector is established.On this basis,the expectation maximization method into random signal detection in atmospheric laser communication,proposes and validates the expected maximum likelihood sequence detection algorithm based on maximum,the working principle of the algorithm is analyzed in detail,and its detection performance in the simulation verification.Finally,the short and medium distance real atmosphere laser transmission experiment is carried out,the proposed algorithm is used to process the data.The experimental results show that the maximum likelihood sequence detection algorithm based on expectation maximization can effectively reduce the influence of noise.The error rate of the system is greatly reduced compared with the data without detection,which improves the accuracy of signal detection,and the computational difficulty is much lower than that of maximum likelihood sequence detection,which has a high practical value.