The Research On Electrical Equalization Algorithm In Optical Coherent Receivers

With the continual development of information society, the substantial requirement of high-quality and high-speed data services sets the new request for transmission system capacity, especially for backbone networks. Therefore, in order to enhancing system capacity, transmission technology base on 100Gb/s in single channel is widely studied in optical fiber communication area.In recent years, polarization-division multiplexing system with optical coherent receivers based on digital signal processing (DSP) has been increasingly concerned and emphasized for long-haul transmission in a number of new ultra-high speed optical transmission technology. Not only does it improve the spectral efficiency and double the information rate by using multilevel modulation formats, but also optical coherent detection contains both amplitude and phase information which allows to compensate impairments flexibly in digital domain.The thesis profoundly investigates optical coherent polarization multiplexing QPSK transmission system with rate of 100Gb/s. And it will be done further research on simulation and design realization of digital signal processing scheme. The work can be divided into four parts.1. The thesis has studied the architecture and implementation of scheme of the PM-NRZ-QPSK coherent optical transmission system. Then the simulation modeling of optical coherent transmission system by VPItransmissionMaker hss presented, which will provide the data source to the follow-up DSP computer off-line processing platforms by Matlab software. 2. The thesis has studied and realized an electrical equalization scheme, which is able to realize linear equalization and polarization de-multiplexing. The two main algorithms for LMS and CMA were compared and the latter was selected as the more advanced process. Then, through analyzing and optimizing the key parameters that have effects on system performance, it found out some important conclusions, which can be used to guide the design of a long-haul backbone system.3. In order to solve the inherent problem for constant modulus algorithm, two modified algorithms were proposed in this thesis. Simulation results showed that two novel algorithms can overcome the phase-blind nature of the conventional CMA and obtain obtained well performance under the conditions of various channel.4. On the other hand, by assessing computational and hardware complexity, it proposed two kinds of parallel processing schemes and one frequency domain filtering method. Then, it showed the effectiveness of the proposed method in simulation.