Research On Technology Of Homodyne Coherent Optical Communication Based On 90° Hybrid

With the advantages of high sensitivity, high-speed, long communication distance and strong anti-interference ability among the satellite inter-satellite communications, homodyne coherent optical communication has become an important development direction of the future research. Under the conditions of ensuring the signal light and the local oscillator phase-locked, the sensitivity level of the quantum limit could be achieved by the homodyne coherent optical communication system. As the key technologies for the optical phase-locked loop, it is very important to select the types of hybrid for the reasons of that optical phase-locked loop and communication system based on different types of hybrid could cause a large difference in the optical communication performance, and it has important research value.This thesis takes the optical phase modulation-BPSK, which could maximize the advantage of high sensitivity of homodyne coherent optical communication system, and the 1064 nm optical phase coherent optical communication as research background to deeply study the homodyne coherent optical communication technology. According to the experimental conditions, this thesis select Balanced loop and Costas loop as the representative to in-depth analysis their working principle and advantages and disadvantages of the 180° hybrid and the 90° hybrid. Influenced by the same noises, when the error rate is 10-9 of the two phase-locked loop homodyne coherent optical communication system, this thesis gets the limit sensitivity respectively are 15photons/bit and 13photons/bit by calculating. And combine with the structural models and the formula derivation, the 90° hybrid is detail theoretical analyzed.Secondly, the degree of influence to the 90° hybrid relative phase difference caused by the laser frequency difference, the optical path difference, the quarter wave-plate, the half wave-plate and the polarizing beam splitter are simulated in the soft of Matlab according to the theoretical analysis results. Subsequently, Costas phase-locked loop based-on 90° hybrid and Balanced phase-locked loop based-on 180° hybrid homodyne coherent optical communication simulated system are built by using the Simulink simulation platform. The communication eye diagrams, limit sensitivity and corresponding bit rate influenced under the same noise of the homodyne coherent optical communication simulated system based-on the two types hybrid are tested. And the results verify the correctness of that the communication performance of 90°hybrid is better than the 180° hybrid homodyne coherent optical communication system.Finally, with reference to the theoretical analysis and simulation results, two types hybrid homodyne coherent optical communication system experimental platform are built. When the communication rate experimentally measured is 1.25 Gbps and the highest communication sensitivity reaches-51 d Bm, at this time the bit error rate is 9.72?10-5 by adjusting the temperature control circuit and PZT control circuit to keep the phase-locked loop in a steady locked situation. Costas phase-locked loop of homodyne coherent optical communication experiment system is built and with the loop is continuous stability phase-locked, it achieves the effects of the initial communication.