Methods for producing optical fiber preforms with low index trenches

Patent metadata

Field	Value
Publication number	US-9873629-B2
Application number	US-201113173777-A
Country	US
Kind code	B2
Filing date	Jun 30, 2011
Priority date	Jun 30, 2011
Publication date	Jan 23, 2018
Grant date	Jan 23, 2018

Abstract

Methods for forming optical fiber preforms with low-index trenches are disclosed. According to one embodiment, the method includes depositing silica-based glass soot on a bait rod to form a low-index trench region of the optical fiber preform. The silica-based glass soot is deposited such that the low-index trench region has a first density. Thereafter a barrier layer having a second density greater than the first density is formed around the low-index trench region. Therafter, an overclad region is deposited around the barrier layer. The bait rod is then removed from a central channel of the trench-overclad assembly. A separate core assembly is inserted into the central channel. A down-dopant gas is then directed through the central channel of the trench-overclad assembly as the trench-overclad assembly is heated to dope the low-index trench region. The barrier layer prevents diffusion of the down-dopant from the low-index trench region into the overclad region.

First claim

What is claimed is:

1. A method for forming an optical fiber preform, the method comprising:
depositing silica glass on a bait rod thereby forming a trench region, wherein the silica glass is deposited such that the trench region has a first density, said first density being less than 0.6 g/cm 3 ;
forming a barrier layer of silica glass around the trench region, wherein the barrier layer of silica glass has a second density that is greater than the first density, said second density being at least 1.75 g/cm 3 ;
depositing silica glass around the barrier layer with the second density thereby forming an overclad region of a trench-overclad structure;
removing the bait rod from a central channel of the trench-overclad structure;
inserting a core structure into the central channel;
placing the trench-overclad structure with the core structure into a consolidation furnace;
heating the trench-overclad structure in the consolidation furnace to a temperature within a range from about 800° C. to about 850° C.; and
thereafter flowing a precursor gas comprising a down-dopant through the central channel of the trench-overclad structure while heating the trench-overclad structure in the consolidation furnace to a temperature within the range from about 1400° C. to about 1500° C., thereby doping the trench region with the down-dopant, wherein the layer of silica glass with said second density mitigates diffusion of the down-dopant from the trench region into the overclad region as the trench-overclad structure is heated to the temperature within the range from about 1400° C. to about 1500° C. thereby adhering the trench-overclad structure to the core structure and forming the trench-overclad structure and the core structure as a solid glass optical fiber preform.

2. The method of claim 1 , wherein the preform comprises a core region.

3. The method of claim 1 , wherein the preform comprises a core region surrounding and in direct contact with an inner clad region.

4. The method of claim 1 , wherein:
depositing the silica glass of the trench region on the bait rod comprises reacting silica glass precursor materials in a flame of a gas-fed burner as the flame is traversed over the bait rod in an axial direction at a first speed, wherein the flame of the gas-fed burner has a first temperature; and
depositing the barrier layer of silica glass with the second density on the trench region comprises increasing a temperature of the flame of the gas-fed burner to a second temperature and decreasing a traverse speed of the flame to a second speed as silica glass precursor materials are reacted in the flame.

5. The method of claim 4 , wherein the traverse speed of the gas-fed burner is decreased to the second speed of less than 1 cm/sec.

6. The method of claim 1 , wherein:
depositing the silica glass of the trench region on the bait rod comprises reacting silica glass precursor materials in a flame of a gas-fed burner as the flame is traversed over the bait rod in an axial direction at a first speed, wherein the flame of the gas-fed burner has a first temperature; and
depositing the barrier layer of silica glass with the second density on the trench region comprises increasing a temperature of the flame of the gas-fed burner to a second temperature and reducing a flow of silica glass precursor materials supplied to the gas-fed burner as the flame is traversed over the bait rod.

7. The method of claim 1 , wherein:
depositing the silica glass of the trench region on the bait rod comprises reacting silica glass precursor materials in a flame of a gas-fed burner as the flame is traversed over the bait rod in an axial direction at a first speed, wherein the flame of the gas-fed burner has a first temperature; and
depositing the barrier layer of silica glass with the second density on the trench region comprises increasing a temperature of the flame of the gas-fed burner to a second temperature, reducing a flow of silica glass precursor materials supplied to the gas-fed burner as the flame is traversed over the bait rod, and decreasing a traverse speed of the flame to a second speed.

8. The method of claim 1 , wherein depositing the barrier layer of silica glass with the second density around the trench region comprises depositing the barrier layer of silica glass with the second density to a radial thickness greater than or equal to about 10 μm and less than or equal to about 400 μm.

9. The method of claim 1 , further comprising flowing a muffle gas around an exterior of the trench-overclad structure as the precursor gas comprising a down-dopant flows through the trench-overclad structure thereby preventing the down-dopant from diffusing into the overclad region through an outer surface of the overclad region.

10. A method for forming an optical fiber preform, the method comprising:
depositing silica glass on a bait rod thereby forming a trench region, wherein the trench region has a first density of less than 0.6 g/cm 3 ;
forming a barrier layer of silica glass with a second density around the trench region with the first density, wherein the second density is greater than the first density, said second density being at least 1.75 g/cm 3 , thereby forming an overclad region of a trench-overclad structure,
subsequently removing the bait rod from a central channel of the trench-overclad structure;
inserting a core structure into the central channel;
consolidating the trench-overclad structure around the core structure, the consolidating comprising down-driving the trench-overclad structure through a hot zone of a consolidation furnace having a temperature between about 1400° C. and about 1500° C.; and
during the consolidating, flowing a precursor gas comprising a down-dopant through the central channel of the trench-overclad structure as the trench-overclad structure consolidates around the core structure, thereby doping the trench region and forming an optical fiber preform.

11. The method of claim 10 , wherein a radial thickness of the barrier layer of silica glass with said second density is from about 10 μm to about 400 μm.

12. The method of claim 10 , wherein the down-driving the trench-overclad structure comprises down-driving the trench-overclad structure through the hot zone of the consolidation furnace at a rate between about 5 mm/min and about 50 mm/min.

13. A method for forming an optical fiber preform, the method comprising:
reacting silica glass precursor materials in a flame of a gas-fed burner as the flame is traversed over a bait rod in an axial direction at a first speed thereby depositing silica glass on the bait rod thereby forming a trench region of the optical fiber preform, the trench region having a first density, said first density being less than 0.6 gm/cm 3 ;
increasing a temperature of the flame of the gas-fed burner and decreasing a traverse speed of the gas-fed burner to a second speed thereby forming a barrier layer of silica glass with a second density around the trench region, wherein said second density is greater than said first density, said second density being greater than 1.75 gm/cm 3 ;
depositing silica glass on the barrier layer of silica glass with a second density to form an overclad region of the optical fiber preform thereby forming a trench-overclad structure;
removing the bait rod from a central channel of the trench-overclad structure;
inserting a core structure into the trench-overclad structure;
placing the trench-overclad structure with the core structure into a consolidation furnace; and
thereafter flowing a precursor gas comprising a down-dopant through the central channel of the trench-overclad structure while h

Assignees

• Dawes Steven Bruce
• Knowlton Robert A
• Tandon Pushkar
• Wang Ji
• Corning Inc

Inventors

• Dawes Steven Bruce
• Knowlton Robert A
• Tandon Pushkar
• Wang Ji

Classifications

• C03B2201/12

  doped with fluorine (C03B2201/14 takes precedence) · CPC title

• C03B2207/66

  Relative motion · CPC title

• C03B2207/36

  Fuel or oxidant details, e.g. flow rate, flow rate ratio, fuel additives · CPC title

• C03B37/01453

  for doping the preform with flourine · CPC title

• C03B2203/22

  Radial profile of refractive index, composition or softening point · CPC title