A comprehensive ray approach for teaching intermodal dispersion of a parabolic index profile fiber

A simple and comprehensive ray approach for teaching intermodal dispersion of a parabolic index fiber is proposed. The result is the same as that by using the conventional approach. Because the approach here only uses the ray concepts with very simple mathematics, it can be easily understood by sophomore students. A simple perturbation idea adopted in this paper makes the calculation easier and the distinction between the concepts of near axial and far-axial rays makes the solution have more physical significance.