Nonlinear transmission of a single-mode optical fiber with a sharp change of core diameter

Nonlinear transmission of a cylindrically symmetric weakly guiding single-mode optical fiber with a sharp change of core diameter is estimated in the approximation of weak nonlinearity of the fiber material and is calculated by direct numerical simulation of light propagation. It is shown that an increase or a decrease of nonlinear transmission in comparison with the linear value depends on the way in which the width of the radial mode distribution changes with changing diameter of the structure. Domains of fiber diameters corresponding to an increase of nonlinear transmission in comparison with the linear value are determined. (C) 2000 MAIK "Nauka/Interperiodica".