Surface irregularities on a waveguide are influenced by material composition, the process by which polymer was made, and the technique used to fabricate the end-face. Different end-face preparation techniques (laser ablation, sawing, cleaving, reactive ion etching) produces different kind of surface terrain. Surface features, big compared to the wavelength of light, are represented as phase distortions superimposed on the Gaussian excitation beam, optimized to get maximum coupling efficiency. Similarity between the excitation beam and the fundamental waveguide mode is a measure of coupling loss due to different type of surface errors. To investigate the effect of surface roughness on coupling efficiency, several different surfaces were considered. These included sinusoidal phase gratings, spherical groove, cylindrical groove, wedges and delamination of the waveguide layers. For each tupe of surface error, a critical parameter was identified, and the associated value for that parameter was determined for a given tolerable coupling loss.