Developments in the theory of equivalent-step-index fibers

The equivalent-step-index fiber method rests on the concept that properties of the fundamental mode are not very sensitive to refractive-index profile details. We show how this idea may be incorporated into the original mathematical scheme of Snyder and Sammut [ J. Opt. Soc. Am.69, 1663 ( 1979)] in order to simplify greatly the calculations and to provide wavelength-independent equivalent step-index parameters. The new approach uses the effective waveguide parameter and the moments of the profile-shape function.