Damage Analysis And Compensation Technology Forhigh Speed And High-order Coherent Optical Communitaon Systems

The rapid development of information services leads to the continuously rising demand on the communications network bandwidth and speed.Digital coherent optical communication technology based on high-order modulation,coherent detection and digital signal processing provides a potential solution to the increasing demand on bandwidth and speed requirements of communication systems.The digital coherent optical communication technology fused with coherent detection and digital signal processing not only improves the receiving detection sensitivity of the communication system,applies to a variety of modulation formats,but also can compensate for the electric field damage of received signal,which has the advantages of high flexibility and low cost and makes it a system of great potential for development.The high-order modulation technology can directly and effectively improve the spectrum utilization of the communication system and expand the communication capacity of the single-channel system,which has also attracted high attention of researchers in recent years.In addition,the security of optical fiber communication system has been attracting much attention.Quantum noise random encryption is a technique that uses quantum noise to encrypt signals randomly in physical layer.It has high security and can realize the encryption for high-speed long-distance optical transmission system,which is also favored by much of the researchers in recent years.In this dissertation,the development status and research hotspots of high-order coherent optical communication technology and quantum noise stream coding technology both at home and abroad are extensively investigated.The transmission performance simulation and compensation algorithm of high-order QAM and QNSC coherent optical communication system are studied emphatically.The main research works of this dissertation are as follows:Firstly,the theoretical analysis and modeling of dual-polarization coherent optical communication system are carried out.The numerical simulation platform of 28 GBaud polarization multiplexing digital coherent optical communication system is established by using MATLAB.Secondly,in the channel equalization and de-polarization multiplexing module,a semi-blind equalization algorithm named R-CMA algorithm is proposed according to the characteristics of high-order QAM signals and the existing CMA and MMA algorithms.The Simulation comparative analysis for the equalization effect of the algorithm has been made.The results of the simulation has verified the effectiveness of this algorithm.Thirdly,based on the principle of random encryption of quantum noises,the QPSK signal is successfully encrypted into the high order QAM signal by encoding.The effects of ASE noise,laser linewidth,fiber dispersion and nonlinear effects in coherent optical communication systems on the transmission performance of high-order QAM signals and QAM/QNSC encrypted signals in coherent optical communication systems are simulated and analyzed.It also explored the impact of system damage and the compensation effect of each algorithm.