Ray-mode analysis of a random medium waveguide

Statistical propagation characteristics in a waveguide filled with a randomly fluctuating medium can be modeled in terms of rays and guided modes. In this work, a plane-parallel waveguide filled with a random medium having a characteristic fluctuations scale much smaller than the transverse waveguide dimension is considered. The field approaching the observer in such a waveguide can be approximated as a sum of contributions of a direct ray and the rays reflected by the waveguide walls. The corresponding intensity distribution is presented as a sum of two parts: coherent and incoherent. Using the Poisson summation formula, these portions can be transformed into the sums of guided modes. Numerical examples are presented.