Effect of axial linear and sinusoidal variation of the core refractive index on the propagation of some low-order modes in an optical fiber

Abstract

In this communication, we report the result of a preliminary study of the effect of an axial variation of the core refractive index n1(z) on the propagation of some lower order modes in optical fibers. We take two types of axial variation of n1(z): 1) linear, and 2) sinusoidal. The modal propagation properties are obtained under the weak guidance approximation. The consequent dependence of the propagation parameter β with a z-coordinate is shown for both types of core refractive index dependence on z. We find that, for both a linear and sinusoidal variation of n1(z), β fluctuates, but this happens more smoothly and symmetrically in the latter case.