Research On High Speed Laser Communication Experiment System Based On DPSK/self-homodying Detection

In space laser communication,the sensitivity of the communication system is one of the key factors that restrict the communication rate.Traditional intensity modulation-direct detection methods cannot achieve high-speed long-distance communication.Therefore,countries around the world are exploring communication systems that have higher sensitivity and are suitable for high-speed communications.DPSK communication based on self-homodying detection is considered as one of potential solutions in this area.Both the United States and Japan plan to adopt this solution in the next generation of high-altitude satellite laser communications,achieving an effective data rate of more than 1 Gbps.Therefore,research on DPSK/self-homodying detection high-speed laser communication system has important application value.This paper introduces the principle of modulation and demodulation of DPSK signals and compares the modulation effects of the Li Nb O3 phase modulator(PM)and the Li Nb O3 Mach-Zehnder modulator(MZM).The effect of the operating point drift of the Mach-Zehnder(MZM)external modulator on the performance of the system is analyzed.The importance of the automatic bias control of the modulator is illustrated;the key damage of the receiver to the differential phase shift key is analyzed.The effects of the DPSK/self-homodying detection system performance,such as the imbalance of the receiver's balanced photodetector,unbalanced reception time,mismatch of the MZI delay time and bit period,and frequency offset of the laser and delay line interferometer ?f.Finally,the overall design of the system was carried out,and a communication system based on DPSK/self-homodying detection was set up.The high-speed communication method was studied through experiments.Through experiments,the light path of the transmitter and the receiver was set up,verifying the possibility of 10 Gbps high-speed communication.