Optical waveguides are formed by implantation of various ions (H+,H2+,He+,Li+, andB+) in fused quartz and the properties of mode propagation are investigated at 6328 Å. The origin of the refractive index change is discussed from the ESR measurement. The depth distribution of defects is measured by ESR measurements and the effective thickness of the high-refractive index region is estimated from the measured depth distribution of defects. In as-implanted samples, the propagation loss decreases with decreasing fluence, but a minimum fluence is required for a given implantation energy for the lowest mode to be propagated. The propagation loss is explained to be internal absorption due to color centers introduced by ion implantation. It is shown that the propagation losses are different for various implanted ions. Annealing behavior of the propagation loss and the refractive index change is also presented.