  Exact calculations of transmission and reflection coefficients in surface
randomly corrugated optical waveguides are presented. As the length of the
corrugated part of the waveguide increases, there is a strong preference to
forward coupling through the lowest mode. An oscillating behavior of the
enhanced backscattering as a function of the wavelength is predicted. Although
the transport is strongly non isotropic, the analysis of the probability
distributions of the transmitted waves confirms in this configuration
distributions predicted by Random Matrix Theory for volume disorder.
