Impact of Polarization-Mode Dispersion on Fiber Nonlinearities

University Of Rochester, Rochester NY

Investigators

Abstract

0320816 Agrawal Even though the polarization-mode dispersion (PMD) phenomenon has been studied extensively in recent years, most of the research on PMD has been carried out within the linear approximation in which all fiber nonlinearities are neglected. Although this approach has provided considerable physical insight, it cannot be used for real lightwave systems in which nonlinear effects such as self- and cross-phase modulation (SPM and XPM) are not generally negligible. For the same reason, it cannot be used in the soliton regime where the nonlinear effects are used for sustaining solitons. What is needed is a comprehensive research program that studies the impact of PMD on various nonlinear effects such as SPM, XPM, four-wave mixing (FWM), and stimulated Raman scattering. The primary goal of the proposed research is to develop a new theoretical framework that is capable of including the impact of PMD on several important nonlinear effects occurring inside optical fibers. More specifically, we plan to study the impact of PMD on SPM, XPM, FWM, and stimulated Raman scattering. The PMD problem is generally quite complicated because of its stochastic nature. Most of the research so far on PMD has ignored fiber nonlinearities because it considers the state of polarization of each frequency component of the pulse separately. This approach cannot be used for real lightwave systems in which the nonlinear effects are not generally negligible. To remedy this situation, the PI proposes a research program in which the PMD effects will be incorporated by solving the underlying nonlinear Schrodinger equation with the moment method. This technique will allow us to find the stochastic but ordinary differential equations for several important pulse parameters such as the position, width, chirp, and energy. A somewhat different approach is needed for handling the PMD effects on FWM and stimulated Raman scattering. These two nonlinear effects are increasingly being used for making parametric and Raman amplifiers. Fiber lengths used for making such amplifiers are long enough that PMD effects cannot be ignored. The PI has already begun to focus on the Raman-amplification problem and has developed a simple model that allows the PI to find the average and standard deviation of the PMD-induced fluctuations in the amplified signal. He plans to extend this technique to the case of parametric amplification. Although most of the proposed research is of theoretical nature, the PI intends to verify the theoretical predictions in collaboration with other experimental groups.