MODAL DISPERSION-CURVES OF AN OPTICAL WAVE-GUIDE WITH AN ANNULAR CORECROSS-SECTION SEPARATED BY 2 NONCONCENTRIC CIRCLES FROM 2 CLADDING REGIONS

An optical fiber with an annular cross section bounded by two nonconce ntric circles is analytically studied with a view to obtaining the mod al 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 o f numerical computations. The curves corresponding to some modes are s imilar to the standard dispersion curves for waveguides. However, the dispersion curves of other modes show some unexpected behavior; one mo de even shows no dispersion at all. These points are qualitatively dis cussed. (C) 1997 John Wiley & Sons, Inc.