NONLINEAR MODAL PARAMETERS OF OPTICAL FIBERS - A FULL-VECTORIAL APPROACH

Nonlinear propagation constants and related nonlinearity coefficients of the fundamental modes of tapered fibers and step-index elliptical-c ore fibers are determined by the use of a new numerical approach for s olving vectorial Maxwell's equations, assuming a Kerr-type nonlinearit y. A numerical method based on a finite-element scheme and the iterati on procedure are reported. Nonlinear modal parameters computed from so lutions of the scalar Helmholtz equation and vectorial Maxwell's equat ions are compared with those obtained by the use of scalar and vectori al first-order perturbation methods. For both devices, the limitation of the scalar approach is clearly demonstrated. For tapered nonlinear fibers, the validity of the full-vectorial first-order perturbation me thod for some ranges of the input power is established. Physical inter pretation of the results and their potential applications are given. ( C) 1995 Optical Society of America