Space Coherent Optical Communication Decision Feedback Phase-locked Loop

Compared with traditional microwave communication, free space opticalcommunication (FSOC) has more superiorities such as much greater communicationcapability, low power dissipation, good anti-interference ability, less device size, highsecrecy, and high capability of anti-electromagnetic disturbances. In space coherentlaser communication system, detection sensitivity can be greatly improved,bandwidthadvantages of space optical communication can be reflected well,urpassing thetraditional intensity modulation/direct detection (IM/DD),which makes coherent lasercommunication a most valuable research subject. For optical phase locked loop(OPLL)provides local vibrating laser with completely same frequency and same phase for thehomodyne detection,it has become the key research object of space coherent detection.Basic concept of space coherent optical phase lock loop and it’s research situationwere introduced in this thesis. On the foundation of general Phase lock loop theory andstructure, combined with the characteristics of space coherent laser communications,a kind of optical Phase lock loop called decision feedback Phase lock loop used in theBPSK (BPSK: Binary Phase Shift Keying) modulation/homodyne detection wasdesigned.In this thesis,the basic components involved the frequency mixer, the phasediscriminator, loop filter and tunable laser emitter of decision feedback and phase lockloop were expounded, function and the mathematical model of every part of the loopwere analysed. An system model of optical decision feedback and phase lock loop wasestablished. By using the theory of optical communication, automatic control and phaselock loop, firstly the signal characteristics, signal power, signal bandwidth, loopbandwidth and noise bandwidth was presented and elaborated,then the transfer functionof the loop was given from which zero&pole distribution could be observed andfrequency response could also be got. Finally, the module level simulation experimentconducted. The key research of this thesis is the cause of the phase locked error. Bymeans of the equation of the Inter-satellites optical coherent communication link, thisthesis made a study on the influence to performance of receiving. On the basis of aseries of numerical calculation as well as MATLAB and ADS simulation, preliminary design, overall thought and main parameters of the decision feedback phase lock loopfor the space coherent optical communication were put forward.By theoretical calculation and simulation testing, a conclusion that the decisionfeedback phase lock loop can realize fast optical phase lock with a locked error of5degrees has been obtained. As a result, the loop can be able to provide space coherenthomodyne detection with local vibrating laser, satisfying the requirement of OSC.