Multi-level Phase Modulation Formats And Their Phase Regeneration In High Speed Fiber-optics Communication System

Multi-level phase modulation format is the industry-recognized first choice of modulation format for the next generation high-speed fiber-optics communication system. Phase noise, especially the nonlinear phase noise is one of the main factors which cause the receiver sensitivity reduced for DPSK and DQPSK systems. Either coherent receiver or the direct receiver can they not eliminate or reduce the impact of nonlinear phase noise on the system. Therefore, it is necessary to take certain measures to reduce the phase noise before the receiver for systems with large nonlinear phase noise, which means to recovery the phase information of the signal or realize the phase regeneration.This dissertation focuses on theoretical analysis, numerical simulation and experimental demonstration for multi-level phase modulation format as well as their phase jitter features and phase recovery techniques. In this dissertation, the structure of the regenerator is designed and optimized; the regenerative effects of regenerator are numerically simulated; finally, a phase regenerator with relatively simple structure and excellent performance is experimentally realized. The research in this thesis has important theoretical significance and practical value for the realization of next generation all-optical and high-speed optical fiber communication network.The research works in the dissertation are summarized as follows (innovative works are labeled in bold):(?) Modulation technology of optical signal is reviewed; Mach-Zehnder modulator which is extensively used in optical modulation is analyzed; characteristic of time and frequency domain for DPSK and DQPSK modulation format is analyzed both via theoretical analysis and numerical simulation, including constellation, phase diagram, eye diagram and spectrum of different duty-cycle signals.(?)The concepts and representation of phase noise, as well as the cause and compensation methods of phase noise are theoretically analyzed; The numerical simulation of the different types of phase noise is made, which lays a theoretical foundation for the phase regeneration.(?) The principles of several different kinds of phase regeneration technologies are introduced, and their advantages and disadvantages are analyzed.(?) The mathematical model of phase regenerator is established theoretically and its system structure is analyzed; phase regeneration system based on semiconductor optical amplifier is studied via theoretical derivation, design and construction of simulation platform and a series of parameter optimization.(?) A peripheral driver circuit of the semiconductor optical amplifier (SOA) is designed and implemented, which provides the necessary hardware preparation for the implementation of phase regeneration experiments; the saturated gain characteristics, the polarization sensitive features and related parameters of SOA are studied via experiments.(?) Phase regenerator is applied to DPSK and DQPSK system, and the phase regeneration experimental system for DPSK signals is designed and set up; The spectrograms and eye diagrams of DPSK signals before and after phase regeneration are achieved via experiments, which verifies the performance of phase regeneration for this scheme.