Abstract: An improved MCVD process reduces a rippling structure in the refractive-index profile of a graded-index, multiple-mode optical fiber by incorporating N2O, CO, or NF3 gas in the gas stream during deposition of a soot sub-layer from which the optical fiber is formed. The soot sub-layer is sintered to form a glass sub-layer during deposition of a subsequent soot sub-layer. A dopant species is incorporated in each soot sub-layer during deposition. Fibers made from the doped glass sub-layers have a graded refractive-index profile that is near-parabolic in shape and that has significantly reduced rippling compared to profiles observed for fibers prepared conventionally.