# US 4,367,013 A · Preparation of semifinished product for manufacture of optical fibers

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 4,367,013 A
- Document ID: US4367013A
- Status: Granted
- Kind: A
- Application number: 06/233,512
- Filed: 1981-02-11
- Granted: 1983-01-04
- Earliest claimed: 1980-02-15
- Assignees: Quartz & Silice
- Inventors: Pierre Guerder; Andre Ranson
- Web page: https://patentgrep.com/patent/US4367013A

## CPC

- C03B 37/01426: {Plasma deposition burners or torches}
- C03B 37/014: made entirely or partially by chemical means {, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] (C03C17/02 takes precedence)}
- C03B 37/01413: {Reactant delivery systems (C03B37/01807 takes precedence; devices therefor in general B01D1/00, B01J4/00)}
- C03B 37/01823: {Plasma deposition burners or heating means}
- C03B 2201/12: doped with fluorine (C03B2201/14 takes precedence)
- C03B 2201/42: doped with titanium
- C03B 2207/86: by bubbling a gas through the liquid
- C03B 2207/87: Controlling the temperature
- Y10S 65/16: Optical filament or fiber treatment with fluorine or incorporating fluorine in final product
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A process is described for making a doped-silica ingot useful in the manufacture of optical fibers. At least a silicon compound and a titanium compound are decomposed in the flame of the induction plasma burner in the presence of a determined supply of hydrogen and are reacted with the oxygen contained in the burner feed gas and/or in the vector gas to form SiO.sub.2 and H.sub.2 O against a heat-stable support. As a result silica and titanium oxide are deposited on the support in the form of a homogeneous vitreous mass exhibiting a selected concentration of hydroxyl groups between 10 and 50 parts per million. Fluorine-doped silica is deposited radially in the same way on the resulting ingot. The resulting semifinished product is a cylinder consisting of a titanium-doped silica core, whose TiO.sub.2 concentration by weight is about 0.1 to 8%, covered by a sheath of fluorine-doped silica, whose fluorine concentration is about 0.1 to 3%.

## Claims

### Claim 1

A process of making optical fibers from doped silicas comprising the steps of:
forming a cylindrical ingot by axial deposition, on a heat-stable support, of titanium-doped silica obtained by decomposition and oxidation of at least a silicon compound and a titanium compound in the flame of an induction plasma burner, at least one of said compounds containing a predetermined supply of hydrogen,
coating said ingot surface by a radial deposition of at least a doped silica so that the index refraction of this silica is less than that of the ingot, and
drawing the ingot thus coated into the shape of fibers of narrow diameter,
wherein, during the first step, the silicon and titanium compounds are decomposed and oxidized to form SiO.sub.2, TiO.sub.2 and H.sub.2 O and the supply of hydrogen is determined so as to deposit directly on said heat-stable support a vitreous mass having a concentration of hydroxyl groups between 10 and 50 parts per million.

### Claim 2 (depends on 1)

The process of claim 1 wherein gaseous silicon and titanium compounds are injected on the outside of the burner and penetrate the plasma flame crosswise.

### Claim 3 (depends on 1)

The process of claim 1 wherein the total hydrogen content of the compound or compounds sent in to the flame of said burner is such that concentrations of hydroxyl groups in the doped silica are between 20 and 30 parts per million.

### Claim 4 (depends on 1)

The process of claim 1 wherein the silica is formed from the decomposition and oxidation of a mixture of silicon tetrachloride (SiCl.sub.4) and trichlorosilane (SiHCl.sub.3).

### Claim 5 (depends on 1)

The process of claim 1 wherein the titanium is supplied by at least one of the compounds selected from the group consisting of titanium tetrachloride, isobutyl titanate, and isopropyl titanate.

### Claim 6 (depends on 5)

The process of claim 5 wherein the amount of titanium injected in the plasma is such that the resulting vitreous silica contains a weight percentage of TiO.sub.2 between 0.1 and 8%.

### Claim 7 (depends on 1)

The process of claim 1 wherein during the step of coating the ingot surface by radial deposition there is deposited on the titanium-doped silica ingot a fluorine-doped silica whose weight content in fluorine is between 0.1 and 3%.

### Claim 8 (depends on 7)

The process of claim 7 wherein between the titanium-doped silica core and the florine-doped silica periphery there is radially deposited an intermediate layer made up of silica simultaneously doped with titanium and fluorine.

### Claim 9 (depends on 8)

The process of claim 8 wherein during formation of the intermediate layer the composition of the gaseous mixture is modified by progressively reducing the delivery of the titanium compound or compounds relative to the delivery of the fluorine compound.

### Claim 10 (depends on 7)

The process of claim 7 wherein the fluorine is supplied by at least one of the compounds selected from the group consisting of sulfur hexafluoride and nitrogen trifluoride.

### Claim 11

In the manufacture of optical fibers using doped silicas, a process for making a doped ingot comprising the steps of:
forming a cylindrical ingot by axial deposition, on a heat-stable support, of titanium-doped silica obtained by decomposition and oxidation of at least a silicon compound and a titanium compound in the flame of an induction plasma burner, at least one of said compounds containing a predetermined supply of hydrogen, and
coating said ingot surface by a radial deposition of at least a doped silica so that the index of refraction of this silica is less than that of the ingot,
wherein, during the first step, the silicon and titanium compounds are decomposed and and oxidized to form SiO.sub.2, TiO.sub.2 and H.sub.2 O and the supply of hydrogen is determined so as to deposit directly on said heat-stable support a vitreous mass having a concentration of hydroxyl groups between 10 and 50 parts per million.

### Claim 12 (depends on 11)

The process of claim 11 wherein gaseous silicon and titanium compounds are injected on the outside of the burner and penetrate the plasma flame crosswise.

### Claim 13 (depends on 11)

A doped ingot for use in manufacturing optical fiber formed in accordance with claim 11 and comprising:
a core of titanium-doped silica that is approximately 30 to 50 millimeters in diameter, said titanium constituting about 0.1 to 8% by weight of the silica; and
a sheath of fluorine-doped silica surrounding said core, the total diameter of said core and sheath being approximately 50 to 120 millimeters, said fluorine constituting about 0.1 to 3% by weight of the silica of said sheath.

### Claim 14 (depends on 11)

The process of claim 11 wherein the silica is formed from the decomposition and oxidation of a mixture of silicon tetrachloride (SiCl.sub.4) and trichlorosilane (SiHCl.sub.3) and the titanium is supplied by at least one of the compounds selected from the group consisting of titanium tetrachloride, isobutyl titanate, and isopropyl titanate.

### Claim 15 (depends on 14)

The process of claim 14 wherein the amount of titanium injected in the plasma is such that the resulting vitreous silica contains a weight percentage of TiO.sub.2 between 0.1 and 8%.

### Claim 16 (depends on 14)

The process of claim 14 wherein during the step of coating the ingot surface by radial deposition there is deposited on the titanium-doped silica ingot a fluorine-doped silica whose weight content in fluorine is between 0.1 and 3%.

### Claim 17 (depends on 16)

The process of claim 16 wherein between the titanium-doped silica core and the fluorine-doped silica periphery there is radially deposited an intermediate layer made up of silica simultaneously doped with titanium and fluorine.

### Claim 18 (depends on 17)

The process of claim 17 wherein during formation of the intermediate layer the composition of the gaseous mixture is modified by progressively reducing the delivery of the titanium compound or compounds relative to the delivery of the fluorine compound.

### Claim 19 (depends on 16)

The process of claim 16 wherein the fluorine is supplied by at least one of the compounds selected from the group consisting of sulfur hexafluoride and nitrogen trifluoride.