Nonlinear effects in elliptical-core few-mode optical fibers

Abstract

We examine the nonlinear interaction between the linearly polarized modes on a few-mode elliptical-core optical fiber. Three modes are involved in this process: the fundamental (LP01) mode and the two second-order symmetry modes, LP11 (even) and LP11 (odd), which have slightly different propagation constants. In practical situations the large δβ = β01 − β11(β is the propagation constant) precludes any significant coupling between the fundamental and either of the LP11 modes; however, coupling between the two LP11 symmetry modes may occur for sufficient pump intensities. Exact and approximate analytic expressions are given.