Process for forming a titania-containing preform silica glass blank

• US 6,189,340 B1
• Filed: 10/21/1998
• Issued: 02/20/2001
• Est. Priority Date: 06/17/1996
• Status: Expired due to Fees

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Burke, Gerald Eugene, Truesdale, Carlton Maurice
• Primary Examiner(s): Silverman, Stanley S.
• Assistant Examiner(s): COLAIANNI, MICHAEL
• Application Number:
  US09/171,748
• Time in Patent Office: 853 Days
• Field of Search: 65/386, 65/391, 65/399, 65/421, 65/422, 65/423, 65/424, 65/427
• US Class Current: 65/399
• CPC Class Codes: C03B 2201/42 doped with titanium
• CPC Class Codes: C03B 37/01413 Reactant delivery systems C03B37/01807 takes precedence; devices therefor in general B01D1/00, B01J4/00
• CPC Class Codes: C03B 37/01446 Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering C03B37/01853 takes precedence
• CPC Class Codes: C03C 13/045 Silica-containing oxide glass compositions

Abstract

Disclosed is an optical waveguide fiber having a compressive outer layer that includes TiO₂ in the SiO₂ matrix glass. The compressive outer layer includes crystalline structures containing TiO₂ that are predominately rutile. Also disclosed is a method for making an optical waveguide fiber having a compressive outer layer. The compressive outer layer can contain an additional metal oxide that is preferentially lost from the outer layer, instead of the TiO₂, during the drying and consolidation step.

Claims

1. A process of forming a preform comprising a core portion and a cladding portion surrounding the core portion, said cladding portion having an outer layer and said preform being suitable for consolidation to a glass blank for producing an optical waveguide fiber, said process comprising:

oxidizing a precurser of an additive compound, and Si and Ti containing compounds to form the additive compound, and SiO₂ and TiO₂, and,

forming said preform containing the additive compound, the SiO₂, and the TiO₂, at least in the outer cladding layer of said cladding portion wherein a portion of the TiO₂ present in said preform is in crystalline form with the crystalline form being predominantly rutile.

2. The process according to claim 1 further comprising:

consolidating said preform, after carrying out said oxidizing and said forming, under conditions effective to form said preform into a glass blank.

3. The process according to claim 2, wherein said consolidating is carried out under an atmosphere of a treating gas, wherein said treating gas is selected from the group consisting of helium, oxygen, and chlorine.

4. The process according to claim 3, wherein by the process comprising:

the additive compound is preferentially sacrificed instead of TiO₂, when consolidating said preform.

5. The process according to claim 1 wherein the additive compound causes more of the crystalline TiO₂ present in the preform to be rutile in comparison to the amount of rutile present in a similar preform made using a process which does not include the additive compound.

7. The process according to claim 1, 4, or 6, wherein the additive compound is a metal oxide compound, said metal being selected from the group consisting of Sn, Pb, Bi, Sb, and mixtures thereof.

12. The process according to claim 4 or 6 wherein said consolidating is carried out at a temperature of 900°

to 1400°

C.

6. A process for reducing depletion of TiO₂ from an SiO₂—

TiO₂ containing glass blank during formation of said glass blank from a preform having a porous outer layer, which during said formation becomes the outer layer of the glass blank, comprising;

oxidizing Si and Ti containing compounds and a precurser of an additive compound to form SiO₂—

TiO₂, and the additive compound;

forming a preform containing, at least in the outer porous layer, the SiO₂, the TiO₂, and the additive compound; and

consolidating the preform under conditions effective to form a glass blank, wherein said additive compound is effective to reduce depletion of TiO₂ in at least the outer layer of said glass blank during said consolidation.

8. The process according to claim 6 wherein said step of forming a preform is carried out by an outside vapor deposition process or a vapor axial deposition process.

9. The process according to claim 6, wherein said additive compound is SnO₂ comprising about 0.1 to 10 weight percent of said porous outer cladding layer.

10. The process according to claim 6, wherein the outer cladding layer of said class blank has a TiO₂ concentration no more than about 3 weight percent less than the TiO₂ concentration of said porous outer cladding layer of said preform.

11. The process according to claim 6, wherein said porous outer cladding layer of said preform comprises about 8 to 20 weight percent TiO₂, and said outer cladding layer of said glass blank comprises about 5 to 17 weight percent TiO₂.

13. The process according to claim 6, wherein said additive compound is SnO₂ comprising about 1 to 2 weight percent of said porous outer cladding layer.

14. The process according to claim 6, wherein said porous outer cladding layer of said preform comprises about 11 to 13 weight percent TiO₂, and said outer cladding layer of said glass blank comprises about 8 to 10 weight percent TiO₂.