Perturbation theory for the evaluation of the normalised cutoff frequencies in radially inhomogeneous fibres

Abstract

A simple perturbation theory has been used to study the normalised cutoff frequencies of radially inhomogeneous fibres. The formalism has been developed with a truncated parabolic-index profile as zero-order solution. Numerical calculations have been carried out for α-profiles and have been found to be in good agreement with more rigorous approaches reported by previous authors.