Design And Implement Of The Transmitter In Coherent Optical Communication System

The optical coherent detection technology can greatly improve the signal detection sensitivity, optimize the frequency selectivity of signal processing system, and enhance the anti-interference ability of signal transmission. Coherent optical communication system with heterodyne detection or homodyne detection has longer unrepeated transmission distance compared with ordinary optical communication system with intensity modulation-direct detection, which is more beneficial to the complete utilization of the fiber bandwidth and the improvement of transmission performance.An appropriate DPSK transmitter design scheme for coherent optical communication system is proposed based on the mathematical modules of optical transmitter. Lithium niobate modulator and narrow band single mode laser are mainly used in this scheme and they can be applied to realize NRZ, RZ-33, RZ-50, CSRZ and DPSK modulation formats.Besides, a laser diode module with a monolithically integrated electro-absorption modulator is discussed in the paper. Driving circuit for the electro-absorption modulator and control circuit for the laser are designed and a simple NRZ modulation format is realized using this laser diode module.Firstly, generation technology of different modulation formats is analyzed to support the design of the transmitter. Then, the perspective of principal diagram design, the design rules for high-speed PCB and points for attention are discussed. Finally, the testing results were given in the paper. The emphases and difficulties of the hardware design are the design of laser driving current and that of the placement and routine of high-speed PCBs of 2.5G and 10G...