Compensation Technology Of Doppler Frequency Shift In Space Coherent Laser Communication

Coherent detection is better than other detection in the form of sensitivity and so on, has become the focus of research in recent years at home and abroad. At the same time the space coherent optical communication system involves the atmospheric link, so it is different from the coherent optical communication system which in the fiber. Such as Doppler frequency shift caused by the relatively rapid movement of communication terminals makes carrier synchronization worse. Based on the relative positions and velocities between satellites and receiving station, Doppler frequency shift can be pre-estimated.Coherent optical communication on frequency and phase of the signal light and the local oscillating laser requirements are very strict, optical phase-locked loop (OPLL) can solve both the problem of phase synchronization. The OPLL function of each part are introduced in detail, aimed in OPLL mathematic model and simulation. Finally, the various step is simulated.it points out the harm of the random noise of OPLL in the paper..This paper also relates to auxiliary temperature and external input voltage of the oscillator regulation, which can change the output frequency of the laser. Designed a realization of automatic frequency scanning scheme at last. We have demonstrated2.5Gbps coherent homodyne BPSK reciver with a compensator of Doppler frequency shifts. If±7.5GHz frequency offset exists in TX-laser simulated as Doppler shift, the receiver sensitivity has been26photon/bit at BER1E-6.