Research On Key Technologies Of Coherent Optical Communication

According to the difference of coherent receivers, satellite laser communication sys-tems can be divided to coherent and non-coherent optical communications. Early satellite laser communication systems have adopted non-coherent optical communication systems that satisfy a low-bit-rate communication request, but the power of transmitter and sensi-tivity of receiver limit the communication rate. While coherent optical communication system has great advantages in the long-distance, high-speed communications and become the major means of satellite laser communications.Coherent optical communication system has many key technologies to be resolved, such as Doppler frequency shift caused by the relatively rapid movement of communica-tion terminals makes carrier synchronization worse. The phase noise of laser makes it dif-ficult for receiver to demodulate the signal. Atmospheric turbulence causes the outage probability increase. In this thesis, we have proposed some algorithms corresponding to these issues: Doppler frequency shift compensation algorithm, phase noise reduction algo-rithm, multi-beam technology.This thesis chooses BPSK as the modulation of the coherent optical communication and simulates its bit error rate. Against the impact of Doppler frequency shift, This thesis proposed FFT and V&V algorithm and least-squares estimation algorithm. In order to re-duce the impact of phase noise, constrained LMS algorithm is proposed. To overcome at-mospheric turbulence that caused outage probability increase, this paper has introduced a multi-beam technology, and studied the equal gain combination and optimal combination that effectively reduce the outage probability.Based on the theoretical analysis, this thesis has all the algorithms simulated by Mat-lab, respectively. From the results, all the algorithms proposed by this thesis have solved the above problems effectively, achieving the aim of improving the performance of co- herent optical communication system. This thesis has provided theoretical support for the design of coherent optical communication system.