Patent ID: 8037717

Claim:
A method of manufacturing an optical waveguide preform, said method comprising the steps of: providing a first gaseous atmosphere including a first halogen-containing gas to a soot preform contained in a vessel, the first halogen-containing gas being selected from the group consisting of SiF 4 , SF 6 , CF 4 , C 2 F 6 , COF 2 , C 2 F 2 Cl 2 , and F 2 ; maintaining the first gaseous atmosphere between 1100 and 1300° C., for a first reacting time sufficient to at least partially dope the soot preform, wherein the first halogen-containing gas has a partial pressure which decreases during the first reacting time, wherein no more than 0.5 slpm of the first gaseous atmosphere flows out of the vessel during the first reacting time, and wherein the first gaseous atmosphere is pressurized to a gage pressure of at least 0.1 atm gage during the first reacting time; evacuating at least a portion of the first gaseous atmosphere from the vessel; providing the vessel with a second gaseous atmosphere including a second halogen-containing gas, the second halogen-containing gas being selected from the group consisting of SiF 4 , SF 6 , CF 4 , C 2 F 6 , COF 2 , C 2 F 2 Cl 2 , and F 2 ; and maintaining the second gaseous atmosphere between 1100 and 1300° C., for a second reacting time sufficient to further dope the soot preform, wherein the second halogen-containing gas has a partial pressure which decreases during the second reacting time, and wherein the second gaseous atmosphere is pressurized to a gage pressure of at least 0.1 atm gage during the second reacting time; wherein the soot preform is retained in the vessel throughout and between: the step of maintaining the first gaseous atmosphere, the step of evacuating at least a portion of the first gaseous atmosphere, the step of providing the second gaseous atmosphere, and the step of maintaining the second gaseous atmosphere.