Research On Signal's Degree Of Polarization In PMD Compensation Systems

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 optical link will broaden the optical pulse in time domain and worse the inter-symbol interference(ISI), the product of optical signal will also be degraded. PMD also makes degree of polarization(DOP) degraded, This directly impairs the performance of the PMD compensation system. The topic of this thesis is focused on the DOP technique applied to monitor the PMD of the optical link and various factors effect on DOP character.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 Stocks representation. Using fast Fourier transform, the dynamic range and sensitivity of the DOP technique used to monitor the DGD of single channel system have been simulated under various factors, including pulse chirp, duty cycle, extinct ratio, and self-phase modulation.Secondly, Numerical calculation methods are usually more widely applied in the nonlinear Schr(o|¨)dinger equation (NLSE) because if its complexity. The most commonly used algorithm is the split-step Fourier method(SSFM). But in the actual optical communication system, PMD is a random factor and fit for Maxwell distributing. So when we Numerical calculation NLSE, we let PMD join in, and then we change the signal's input power and investigate how the nonlinear factor effect on DOP character.Finally, the performance of DOP technique used in 40Gb/s optical communication system has been simulated with different initial pulse powers. The dependence of the system outage probability on signal's peak power and transmission distance has also been investigated. This is helpful for system design and the configuration of PMD compensators.