Modal dispersion curves of an optical waveguide with an annular core cross section separated by two nonconcentric circles from two cladding regions

Abstract

An optical fiber with an annular cross section bounded by two nonconcentric circles is analytically studied with a view to obtaining the modal characteristics. Using the characteristic equation derived from the matching of fields at the core-cladding boundaries expressed in terms of bipolar coordinates, dispersion curves are obtained on the basis of numerical computations. The curves corresponding to some modes are similar to the standard dispersion curves for waveguides. However, the dispersion curves of other modes show some unexpected behavior; one mode even shows no dispersion at all. These points are qualitatively discussed. © 1997 John Wiley & Sons, Inc.