Research On Receiving Technology Of Multi-Pixel Photon Counter Array In Deep Space Optical Communication

In deep space optical communication,Pulse Position Modulation(PPM)and photon detector array are widely used with high energy efficiency and detection efficiency.Laser signals are affected by atmospheric turbulence and background light in deep space channel during transmission,which results in the expansion,fragmentation and intensity scintillation of optical signals at the receiver.In this thesis,the receiving scheme is improved and optimized according to the characteristics of optical signals at the receiver.Firstly,as to the uneven distribution of optical signals received by detector array in traditional direct detection and reception scheme based on focal plane,a receiving scheme based on collimation is proposed in this thesis.In this scheme,a pinhole aperture is placed at the focal plane of the receiving antenna.The laser signal passes through the aperture and then reaches the photon detector array through the collimating mirror.Compared with the traditional receiving scheme based on direct detection of focal plane,the optical signal arriving on the photon detector array after collimating mirror in this scheme is more uniform.In addition,aiming at the interference of background light,the aperture size of aperture will be optimized in this scheme,and the optimal aperture size corresponding to different conditions can be obtained,so as to suppress the interference of background light effectively.The simulation results show that the performance of the collimation-based receiving scheme is obviously improved when the background light is larger and the turbulence is stronger.The optimal aperture size varies with the background light and turbulence conditions.Secondly,Multi-Pixel Photon Counter(MPPC)is a high-performance photon detection module with array structure,which can realize single-photon detection and has a large effective detection area.In this thesis,a new array receiving scheme based on a single MPPC is proposed.This scheme mainly transmits the optical signals received by multiple antennas on the universal bracket to an effective detection area of MPPC through multimode fibers.Compared with the array receiving scheme using multiple MPPCs,the new array receiving scheme not only saves the number of photon detectors greatly,but also reduces the influence of dark counting of detectors effectively.The simulation results show that the system performance of the new array receiving scheme based on single MPPC is better when the background light is small.Finally,in this thesis,a laser communication system is built and tested.In the experiment,the photon counting problem of MPPC is solved firstly,and then a method based on direct prediction of frequency offset and initial phase offset is adopted to achieve slot synchronization.The receiving scheme with a small aperture and collimator is validated.The experimental results show that MPPC can realize photon counting in very weak light,and the system performance can be improved by adding aperture and collimator.