Potential use of nonlinearity-induced virtual gain on parabolic pulse formation in highly nonlinear tapered fiber system

The objective of this work is to investigate the effect of nonlinearity-induced virtual gain in parabolic pulse (PP) formation by dispersion varying fibers and utilizing this gain over that of dispersion. As chalcogenides show high values of nonlinear coefficient, a dispersion decreasing fiber, named as nonlinearly tapered chalcogenide fiber (NLTCF), is designed here by optimizing different combinations of chalcogenide materials and core radius profiles such that efficient PP can be generated at considerably shorter optimum lengths with respect to the corresponding constant dispersion fiber. With suitable manoeuvring of the nonlinearity-induced virtual gain, a fiber combination consisting of a dispersion increasing fiber and the NLTCF shows enough efficiency to reduce the optimum length significantly. Although the virtual gain due to dispersion dominates over that due to nonlinearity in silica fibers, the situation is completely reversed in the case of specially designed highly nonlinear fibers. When compared to silica-based fibers, these types of fibers perform remarkably better in PP formation at shorter values of optimum fiber length with a higher amount percentage reduction of length making the higher order dispersive terms ineffective as well. (paper)