Design And Performance Study Of Satellite Coherent Laser Chaos Communication System

Compared with the traditional satellite microwave communication,satellite laser communication has the advantages of large information capacity,strong antielectromagnetic interference ability,fast transmission rate,high security and small terminal size,and a lot of research and development have been carried out at home and abroad.Coherent laser communication can make full use of the bandwidth advantage of optical carrier to realize high-speed satellite laser communication.It is the key direction of the future satellite laser communication technology development,and it is now receiving more and more attention from many countries and regions.Although the security of satellite laser communication is higher than that of traditional satellite microwave communication because of the narrow transmitting beam,there is still a risk of eavesdropping.Especially in the downlink,the spot where the beam reaches the receiving surface will spread into a spot with a diameter of several kilometers,and the UAV can fly to the spot area for eavesdropping.At present,satellite laser secure communication is based on key technology,but with the development of quantum computing and cryptography,the security of traditional public key encryption technology has faced great risks.Because chaos is unpredictable and sensitive to the initial value of the system,it has long been paid attention to by researchers in the field of secure communication.The laser chaotic system has higher dimensions and higher security,and can support high data rate communication.As a hardware encryption technology,laser chaos communication can avoid the security risks of software encryption algorithms.Introducing it into satellite coherent laser communication can realize high-speed and safe satellite laser communication.In this paper,a laser phase chaos generator based on Mach-Zehnder interferometer is introduced into satellite coherent laser communication.Aiming at a satellite coherent laser chaotic communication system based on differential phase shift keying(DPSK)/autodyne detection,the parameter design requirements in actual engineering mainly focus on theoretical and simulation analysis from three perspectives: chaos generator,chaos synchronization and communication,and mismatch caused by atmospheric turbulence.First,for the laser phase generator based on the Mach-Zehnder interferometer,the influence of the system parameters on the chaos generation process is analyzed,and the Gauss-like and autocorrelation characteristics of the chaos output of the system are analyzed.The bit error rate model of the eavesdropper is derived and verifies the feasibility of realizing secure communication.Furthermore,the principle of chaos synchronization and communication of the system is explained.The influence of parameter mismatch on the synchronization of the system is studied through numerical simulation and analytical approximation,and the bit error rate model of the effect of mismatch noise on system communication performance is derived.Finally,for the light intensity scintillation and beam drift caused by atmospheric turbulence,the influence of the chaos mismatch caused by these two atmospheric effects on the communication performance of the system is mainly analyzed,and the bit error rate model of the downlink and uplink is deduced.The influence of the main parameters of the system on the bit error rate is analyzed.The research work in this paper will provide theoretical and simulation guidance for the parameters design of satellite coherent laser chaos communication system based on DPSK/self-homodyne detection,and has reference significance in reducing the difficulty of engineering implementation and improving communication performance.