Monitoring And Compensation Of Polarization Mode Dispersion In High Speed Optical Fiber Communication

Polarization-mode dispersion (PMD) has been regarded as a severe, ultimate limitation in high bit-rate/long-distance and high capacity optical fiber communication systems. Because the PMD effect of the optical link will broaden the optical pulse in time domain and worse the inter-symbol interference (ISI), the product of the bit-rate and transmission distance is limited. Due to the PMD, the degree of polarization (DOP) of optical signal will also be degraded. This directly impairs the performance of the optical polarization multiplexing (PM) system. The topic of this thesis is focused on the DOP technique applied to monitor the PMD of the optical link and the impact of the PMD on the PM system.Firstly, a summary of the relating concepts of PMD and its characterization is given. The measurement, monitoring and compensation of the PMD are also described. Based on the first-order assumption, an analytical expression of the DOP, which depends on the differential group delay (DGD) of single-mode fiber, has been derived by using the translation relations between Jones representation and Stokes representation. Using the fast Fourier transform (FFT), the dynamic range and sensitivity of the DOP technique used to monitor the DGD of 20Gb/s optical time division multiplexing (OTDM) system have been simulated under various factors, including pulse chirp, duty cycle, extinct ratio, amplified self-emission noise (ASE) and self-phase modulation (SPM).Secondly, the performance of DOP technique used in 40 and 80Gbs optical communication system has been simulated with different initial pulse shapes. The dependence of the system outage probability on peak power of the optical amplifier and transmission distance has also been investigated. This is helpful for system design and the configuration of PMD compensators.Thirdly, we quantify the power penalty caused by the PMD in optical subcarrier multiplexing (OSCM) system with amplitude shift keying (ASK) and binary phase shift keying (BPSK). The DOP of optical signal, as a function of the PMD of the optical link, has also been simulated. The results show that both signal DOP and power penalty have similar periodic fading with the change of the PMD.Finally, the impact of PMD in optical polarization multiplexing system has also been investigated,In particular, applying Monte Carlo method with importance sampling (IS), we have quantified the power penalty, outage probability, and PMD tolerance of PM system affected by the PMD with different modulation format, including on-off keying (OOK), differential phase shift keying (DPSK), and quadrature phase-shift keying (QPSK). The performance of PM system compensated by a first-order PMD compensator, a polarization controller followed by a variable delay line, has also been simulated. The results show that the higher-order PMD can seriously impair the performance of PM system.