Study of fiber nonlinear effects on fiber optic communication systems

This dissertation studies different effects from the fiber Kerr nonlinearity on optical fiber communication systems with the focus on efficient methods to compute the system degradations from these nonlinear effects.; We first review and develop several analysis tools which are essential to the study of optical fiber systems. These analysis tools focus on solving the nonlinear Schrödinger (NLS) equation that describes the propagation of optical pulses through optical fiber channels. Even though the NLS equation can be solved numerically by the split-step Fourier (SSF) method, analytical solutions like the Volterra series transfer function (VSTF) method are still preferable for system performance evaluation when stochastic parameters of the signal and fiber channel are considered. The modified VSTF methods is introduced to solve the energy divergence problem associated with the truncated third-order VSTF method, offering a more accurate result.; We then study the two most important nonlinear effects, cross-phase modulation (XPM) and four-wave mixing (FWM), in the wavelength-division multiplexing (WDM) systems based on the VSTF method. These two nonlinear effects both cause intensity fluctuation of a channel from its neighboring channels. The same system model is used for the study of both effects and consequently direct comparisons between the two effects is possible in our study. As an indication of the system performance, we compute the variance of the intensity fluctuation for both synchronous and asynchronous WDM systems in this dissertation. Different methodologies to reduce the nonlinear effects based on optimizing the system parameters is also discussed.; Another approach to improve the system performance of WDM systems based on multi-user detection is introduced in this dissertation too. The key idea is to make use of the information carried by the channel correlations due to fiber nonlinearity by the use of multiuser detection. The analysis is significantly complicated by the presence of the photodetector, a square-law device, in the system. Using the Gaussian approximation after its validation, both error performance of the multiuser detector and its asymptotic behavior in such systems are thoroughly studied by upper- and lower-bounds and compared with the conventional single-user detector. (Abstract shortened by UMI.)...