Methods and apparatus for pulsed doping or drying a soot preform

A method of manufacturing an optical waveguide preform, said method comprising the steps of:

• providing a first gaseous atmosphere to a soot preform contained in a vessel, the first gaseous atmosphere including a fluorine-containing gas selected from the group consisting of SiF4, SF6, CF4, C2F6, COF2, C2F2Cl2, and F2;
• maintaining the first gaseous atmosphere between 1100 and 1300° C., for a first reacting time of between about 1 and 60 minutes to at least partially dope the soot preform, wherein the first fluorine-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 at the end of the first reacting time;
• then
• providing the vessel with a second gaseous atmosphere, the second gaseous atmosphere including a fluorine-containing gas selected from the group consisting of SiF4, SF6, CF4, C2F6, COF2, C2F2Cl2, and F2;
• 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 fluorine-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 vessel with the second gaseous atmosphere, and the step of maintaining the second gaseous atmosphere.

A method of manufacturing an optical waveguide preform, said method comprising the steps of:

• flowing a process gas into a vessel to provide a gaseous atmosphere in the vessel about a soot preform, the process gas including a first gas selected from the group consisting of SiF4, SF6, CF4, C2F6, COF2, C2F2Cl2, and F2;
• maintaining the gaseous atmosphere between 1100 and 1300° C., for a reacting time sufficient to at least partially dope the soot preform, wherein the first gas has a partial pressure which decreases during the reacting time, wherein no more than 0.5 slpm of the gaseous atmosphere flows out of the vessel during the reacting time, and wherein the gaseous atmosphere is pressurized about the soot preform to greater than ambient pressure during the reacting time;
• and
• evacuating at least a portion of the gaseous atmosphere from the vessel at the end of the reacting time.

A method of manufacturing an optical waveguide preform, said method comprising the steps of:

• providing a soot preform contained in a vessel;
• adding a quantity of a first gas to the vessel to provide a first gaseous atmosphere to the soot preform, the first gas being selected from the group consisting of SiF4, SF6, CF4, C2F6, COF2, C2F2Cl2, and F2;
• 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 gas has a partial pressure which decreases during the first reacting time, wherein the first gaseous atmosphere is pressurized to a first pressure greater than ambient pressure, and wherein no more than 0.5 slpm of the first gaseous atmosphere flows out of the vessel during the first reacting time;
• then
• adding a quantity of a second gas to the vessel to provide a second gaseous atmosphere to the soot preform, the second gas being selected from the group consisting of SiF4, SF6, CF4, C2F6, COF2, C2F2Cl2, and F2;
• and
• maintaining the second gaseous atmosphere between 1100 and 1300° C., for a second reacting time sufficient to at least partially dope the soot preform, wherein the second gas has a partial pressure which decreases during the second reacting time, wherein the second gaseous atmosphere is pressurized to a second pressure greater than ambient pressure, and wherein no more than 0.5 slpm of the second gaseous atmosphere flows out of the vessel during the second reacting time;
• wherein the soot preform is retained in the vessel throughout and between the step of adding a quantity of a first gas, the step of maintaining the first gaseous atmosphere, the step of adding a quantity of a second gas, and the step of maintaining the second gaseous atmosphere.

A method of manufacturing an optical waveguide preform, said method comprising the steps of:

• providing a soot preform contained in a vessel;
• adding a quantity of a first fluorine-containing gas to the vessel to provide a first gaseous atmosphere to the soot preform, the first gas being selected from the group consisting of SiF4, SF6, CF4, C2F6, COF2, C2F2Cl2, and F2;
• then,
• sealing the vessel gas-tight and maintaining the first gaseous atmosphere between 1100 and 1300° C., for a first reacting time sufficient to dope the soot preform, wherein the first gas has a partial pressure which decreases during the first reacting time as the soot preform is doped, wherein the first gaseous atmosphere is pressurized to a first pressure greater than ambient pressure during the first reacting time;
• then,
• evacuating at least a portion of the first gaseous atmosphere from the vessel;
• then,
• adding a quantity of a second fluorine-containing gas to the vessel to provide a second gaseous atmosphere to the soot preform, the second gas being selected from the group consisting of SiF4, SF6, CF4, C2F6, COF2, C2F2Cl2, and F2;
• then,
• sealing the vessel gas-tight and maintaining the soot preform in contact with the second gaseous atmosphere within the vessel, 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 gas has a partial pressure which decreases during the second reacting time as the soot preform is doped, wherein the second gaseous atmosphere is pressurized to a second pressure greater than ambient pressure during the second reacting time;
• wherein the soot preform is retained in the vessel throughout and between the step of adding a quantity of a first fluorine-containing gas, the step of sealing the vessel gas-tight and maintaining the soot preform in contact with the first gaseous atmosphere, the step of evacuating at least a portion of the first gaseous atmosphere from the vessel, the step of adding a quantity of a second fluorine-containing gas, and the step of sealing the vessel gas-tight and maintaining the soot preform in contact with the second gaseous atmosphere.

A method of manufacturing an optical waveguide preform, said method comprising the steps of:

• providing a soot preform contained in a vessel;
• adding a quantity of a first fluorine-containing gas to the vessel and in contact with the soot preform to provide a first gaseous atmosphere to the soot preform, the first gas being selected from the group consisting of SiF4, SF6, CF4, C2F6, COF2, C2F2Cl2, and F2;
• then,
• interrupting the adding of the first fluorine-containing gas into the vessel and maintaining the soot preform in contact with the first gaseous atmosphere within the vessel, and maintaining the first gaseous atmosphere between 1100 and 1300° C., for a first reacting time sufficient to dope the soot preform, wherein the first gas has a partial pressure which decreases during the first reacting time as the soot preform is doped, wherein the first gaseous atmosphere is pressurized to a first pressure greater than ambient pressure during the first reacting time;
• then,
• evacuating at least a portion of the first gaseous atmosphere from the vessel;
• then,
• adding a quantity of a second fluorine-containing gas to the vessel to provide a second gaseous atmosphere to the soot preform, the second gas being selected from the group consisting of SiF4, SF6, CF4, C2F6, COF2, C2F2Cl2, and F2;
• then,
• interrupting the adding of the second fluorine-containing gas into the vessel and maintaining the soot preform in contact with the second gaseous atmosphere within the vessel, 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 gas has a partial pressure which decreases during the second reacting time as the soot preform is doped, wherein the second gaseous atmosphere is pressurized to a second pressure greater than ambient pressure during the second reacting time;
• wherein the soot preform is retained in the vessel throughout and between the step of adding a quantity of a first fluorine-containing gas, the step of interrupting the adding of the first fluorine-containing gas and maintaining the soot preform in contact with the first gaseous atmosphere, the step of evacuating at least a portion of the first gaseous atmosphere from the vessel, the step of adding a quantity of a second fluorine-containing gas, and the step of interrupting the adding of the second fluorine-containing gas and maintaining the soot preform in contact with the second gaseous atmosphere.