On the analysis of a weakly guiding doubly clad dielectric optical fiber with an annular core

A fairly rigorous analytical treatment of an annular core dielectric optica l fiber is presented, the core of the fiber lying between two concentric cl addings with the outer cladding extended infinitely. For the theoretical ap proach, the approximation of the vanishing refractive-index difference betw een the core and the cladding sections is implemented. The investigation is on the preliminary ground, and a numerical estimation of the modal cutoffs is presented for the said fiber. The effects of the core width cis well as the inner core diameter on the propagation constants beta (c) at field cut offs are presented. Plots are also shown of the variation of beta (c) with the change in the refractive-index values. (C) 2001 John Wiley & Sons, Inc.