| With the further development of global communication network, the rapid rise of wireless Internet and the video based applications becoming more and more popular, the demand of communication flow continues to increase, which putting forward higher request to the backbone optical communication capacity. Based on the DSP technology, on one hand, by supporting complicated higher-order modulation formats, such as QPSK, QAM and OFDM, coherent optical communication can provide a good system performance and higher spectrum efficiency. On the other hand, coherent optical communication can use strong processing power of DSP and take the advantage of mature electric equalization algorithms to compensate the linear or nonlinear damage during the communication. Therefore, it becomes the mainstream receiving technology in100Gbit/s or beyond systems.One hotspot of the coherent communication research in recent years is using electric domain algorithm; with the popularity of PDM system, polarization de-multiplexing algorithms have become an important technology affect system performance. This paper mainly focus on the linear damage compensation algorithms, especially the polarization de-multiplexing algorithms. By in-depth theoretical analysis and simulation, a MICA algorithm for QPSK and16-QAM was proposed.This paper can be divided into following three parts:1. Firstly the basic channel model and the principle of the coherent optical communication system are analyzed. Based on the analysis results, a complete Matlab and Optisystem simulation platform is established, which can be used to research and validate the algorithms.2. The study and simulation of the algorithms for individual modules are carried out, which includes the signal orthogonalization, dispersion compensation and phase recovery. Their performances in simulation system are compared.3. In polarization de-multiplexing module, we proposed a novel modified independent component analysis algorithm in order to overcome the singularity problem of classic constant modulus algorithm and improve the convergence performance of ICA. The results of the algorithms are verified in Matlab simulation system, showing that MICA can provide0.5dB and1dB performance in PDM-QPSK and PDM-16-QAM system respectively, and improve the convergence speed and the tolerance to PDL. |
