Method of making fluorine/boron doped silica tubes

Claim 1

A method of forming a glass article comprising the steps of forming a B 2 O 3 -doped porous glass preform having interconnective pores, heating said preform, flowing through said pores at least two different fluorine-containing gases, one of said gases being a source of fluorine for doping said porous preform and a second of said gases being a sufficient amount of BF 3 to prevent fluorine from reacting with the B 2 O 3 in said porous preform and forming a B 2 O 3 -depleted region therein, and consolidating said porous preform to form a dense glass article doped with fluorine and B 2 O 3 .

Claim 2

A method of forming a glass article comprising the steps of forming a B 2 O 3 -doped porous glass preform having interconnective pores, heating said preform, flowing through said pores at least two different fluorine-containing gases, one of said gases being a source of fluorine for doping said porous preform and a second of said gases being a sufficient amount of BF 3 to prevent fluorine from reacting with the B 2 O 3 in said porous preform and forming a B 2 O 3 -depleted region therein, and consolidating said porous preform to form a dense glass article doped with fluorine and B 2 O 3 .

Claim 10

A method of forming a glass article comprising depositing on a cylindrical mandrel a coating of glass particles comprising SiO 2 and B 2 O 3 , said coating containing interconnective pores, removing said mandrel to form a porous glass preform having an axial aperture, inserting said preform into a consolidation furnace muffle, flowing upwardly through said muffle a muffle gas comprising an inert gas, flowing a fluorine-containing gas mixture into said aperture, at least a portion of said gas mixture flowing outwardly through said pores, said gas mixture comprising (a) a first, boron-free fluorine compound that decomposes to form fluorine which dopes said preform, and (b) a sufficient amount of BF 3 to prevent fluorine from reacting with the B2O 3 in said porous preform and forming a B2O 3 -depleted region near the aperture surface, and heating said preform to a temperature within the consolidation temperature range for a time sufficient to cause said particles to fuse and form a dense glass tube.

Claim 11

A method of forming a glass article comprising depositing on a cylindrical mandrel a coating of glass particles comprising SiO 2 and B 2 O 3 , said coating containing interconnective pores, removing said mandrel to form a porous glass preform having an axial aperture, inserting said preform into a consolidation furnace muffle, flowing upwardly through said muffle a muffle gas comprising an inert gas, flowing a fluorine-containing gas mixture into said aperture, at least a portion of said gas mixture flowing outwardly through said pores, said gas mixture comprising (a) a first, boron-free fluorine compound that decomposes to form fluorine which dopes said preform, and (b) a sufficient amount of BF 3 to prevent fluorine from reacting with the B2O 3 in said porous preform and forming a B2O 3 -depleted region near the aperture surface, and heating said preform to a temperature within the consolidation temperature range for a time sufficient to cause said particles to fuse and form a dense glass tube.

Claim 14

A method of forming a fiber optic coupler comprising depositing on a cylindrical mandrel a coating of glass particles comprising SiO 2 and B 2 O 3 , said coating containing interconnective pores, removing said mandrel to form a porous glass preform having an axial aperture, inserting said preform into a consolidation furnace muffle, flowing a fluorine-containing gas mixture into said aperture, at least a portion of said gas mixture flowing outwardly through said pores, said gas mixture comprising (a) a boron-free fluorine compound that decomposes to form fluorine which dopes said preform, and (b) BF 3 , heating said preform to a temperature within the consolidation temperature range for a time sufficient to cause said particles to fuse and form a dense glass tube having first and second opposite end portions and a midregion, a longitudinal aperture extending from a first end of said tube to a second end thereof, disposing a plurality of optical fibers such that at least a part of each fiber extends into the longitudinal aperture of said glass tube, each of said fibers having a core and cladding, at least that part of each fiber that is located in said tube midregion having no coating thereon, each of said fibers extending beyond at least one end of said tube, collapsing said tube midregion onto said fibers, and stretching the central portion of said midregion.

Claim 15

A method of forming a fiber optic coupler comprising depositing on a cylindrical mandrel a coating of glass particles comprising SiO 2 and B 2 O 3 , said coating containing interconnective pores, removing said mandrel to form a porous glass preform having an axial aperture, inserting said preform into a consolidation furnace muffle, flowing a fluorine-containing gas mixture into said aperture, at least a portion of said gas mixture flowing outwardly through said pores, said gas mixture comprising (a) a boron-free fluorine compound that decomposes to form fluorine which dopes said preform, and (b) BF 3 , heating said preform to a temperature within the consolidation temperature range for a time sufficient to cause said particles to fuse and form a dense glass tube having first and second opposite end portions and a midregion, a longitudinal aperture extending from a first end of said tube to a second end thereof, disposing a plurality of optical fibers such that at least a part of each fiber extends into the longitudinal aperture of said glass tube, each of said fibers having a core and cladding, at least that part of each fiber that is located in said tube midregion having no coating thereon, each of said fibers extending beyond at least one end of said tube, collapsing said tube midregion onto said fibers, and stretching the central portion of said midregion.