Representation of fields in inhomogeneous structured waveguides

In this work we present the results of a study of the possibility of using a homogeneous basis and a new generalization of coupled modes theory to describe non-periodic structured waveguides. It was shown that for the studied inhomogeneities the single wave approximation gives good results. Within the framework of single wave approximation, the fields are represented as the sum of two components, one of which is associated with the forward eigen wave, and the second with the backward eigen wave. But this second component is not a backward wave. Because of the coupling, characteristics of this component are determined by the first component, which is significantly larger than the second.