Abstract: A method of manufacturing an optical waveguide preform includes providing a first process gas atmosphere to a soot preform contained in a vessel. The first atmosphere is held in the vessel for a first reacting time sufficient to at least partially dope or dry the soot preform. The vessel is then at least partially refilled with a second doping or drying atmosphere. The second doping or drying atmosphere is held in the vessel for a second reacting time sufficient to further dope or dry the soot preform.

Abstract: A method of manufacturing an optical waveguide preform includes providing a first process gas atmosphere to a soot preform contained in a vessel. The first atmosphere is held in the vessel for a first reacting time sufficient to at least partially dope or dry the soot preform. The vessel is then at least partially refilled with a second doping or drying atmosphere. The second doping or drying atmosphere is held in the vessel for a second reacting time sufficient to further dope or dry the soot preform.

Abstract: The invention relates to the manufacturing of a preform having at least one fluorine doped region. One method of the invention for producing the fluorinated preform includes heat treating a porous soot preform, the preform substantially devoid of any sintered glass layer, to a temperature of greater than about 1200° C. The method further includes exposing the preform to an atmosphere comprising a fluorine containing compound, wherein the time and the temperature of said exposing step is controlled so that &PHgr; comprises≧about 1 wherein &PHgr; is defined as Rmax/(D/k)½, wherein Rmax is the outer radius of the preform, D is the diffusion coefficient of the fluorine containing compound into the preform, and k is the reaction rate constant of the reaction between the fluorine and the soot, thereby controlling the radial penetration of fluorine into the preform.