High-Speed Optical Dual-Polarization Phase Modulation System And Its Polarization Mode Dispersion Compensation

The ever-increasing demand for communication capacity has been pushing the development of the high-speed optical-fiber systems. In recent years, polarization division multiplexing combined with multilevel modulation formats is applied to upgrade the existing system. However, as the transmission speed increases, some factors such as chromatic dispersion (CD)、non-linear effects and polarization mode dispersion (PMD) are critical limitations. Moreover, greater OSNR is required as the level of advanced modulation scheme increases. It becomes significant to overcome the signal distortion and to low the OSNR requirement. In this thesis, novel dual-polarization phase shift keying systems are proposed and analyzed. PMD is mainly considered and PMD compensation for the system is accomplished. In addition, forward error correction is preliminarily discussed in order to decrease OSNR reqirement. The research work is summarized as follows:Modulation technology and the widely-used Mach-zehnder modulator (MZM) and Mach-Zehnder delay interferometer (MZDI) are reviewed and analyzed. By applying these components’mathematical model, the modulation and demodulation processes of some typical modulation formats such as DPSK、DQPSK and QAM are simulated, and some performances including frequency spectrums, phases diagrams and eyediagrams are obtained.PMD compensation technologies including electronic and optical methods are in discussed detail. The optical PMD compensation scheme is deeply investigated. The Degree of polarization (DOP) feedback signal and PSO searching algorithm are simulated and analyzed.A novel dual-polarization differential phase shift keying (DP-DPSK) system which takes advantage of both polarization and phase to carry information is simulated. And its performances including spectral efficiency, CD and PMD tolerance are analyzed via numerical simulation and compared with DPSK and DQPSK system.A novel dual-polarization differential quadrature phase shift keying (DP-DQPSK) system is proposed which does not need polarization de-multiplexing like the conventional PDM-QPSK system. PMD is mainly considered and DOP of the signals is discussed in detail. The results of PMD compensation show that PMD tolerance can be improved by 89ps within 1dB optical signal noise ratio (OSNR) penalty after PMD compensation for the DP-DQPSK system.Initial information formulas for LDPC decoding applied to DPSK and DQPSK system are deduced and analyzed with Mathematics fitting method.