The lossy waveguide as a problem in perturbation theory

A systematic perturbation theory for lossy waveguides is presented. Two possible small dimensionless parameters are identified and introduced into Maxwell´s equations by rescaling pursuant to effecting an expansion of the fields in these parameters. The approximation scheme can be extended to any order of accuracy desired. Although two small parameters are involved in the expansion of the fields in the guide and its walls, the field equations are shown to force the correct ordering of parameters in this expansion