An optimal method to study the propagation characteristics of rectangular optical waveguides

Two methods are presented for the determination of the propagation constants and field distribution of the fundamental and higher order modes of an optical waveguide with a rectangular cross-section and a step index distribution profile. The number of guided modes as a function of the operating wavelength is computed. The interval of a single mode operation is also determined. These methods are the effective index method and the perturbation method. The results of the two methods are compared and satisfactory good agreement between them are obtained. The effective index method is more rapid than the perturbation method where the later needs to calculate some integrals. The perturbation method has accurate results rather than the effective index method but this accuracy is not enough to substitute the time consumed by this method. So, the effective index method is an optimal method to study the propagation characteristics of a rectangular optical waveguide.