Vector theory of the waveguide laser irradiation scattering in an integrated optical waveguide with 3D-irregularities in the presence of a noise is described. For simplification of the analysis of the problem we neglected cross-correlation connections, both between irregularities of the boundaries of the waveguide, and between irregularities of the boundaries and heterogeneities of the refraction index of waveguide mediums. The approximate solution of inhomogeneous three-dimensional wave equation is derived by the Green function method. The analytical formulas of the radiating fields for the propagating and evanescent modes are fined. Physico-mathematical interpretation of derived expressions is given. © 2004 by Astro Ltd.