Analysis of the propagation characteristics of circular step-index fibre with new sheath helix boundary condition

Abstract

A circular step-index fibre with a helical winding on the core-cladding boundary is proposed and investigated analytically with a new type of boundary condition. Using cylindrical coordinate system (r, ϕ, z), new boundary conditions are imposed and longitudinal field components are obtained. The equation involves Bessel and modified Bessel functions. Numerical computations are made. Dispersion curves are obtained for different pitch angles. The main effect of the helical winding on the characteristics is to introduce band gaps.