Halogen-doped silica for optical fiber preforms

Patent metadata

Field	Value
Publication number	US-10947149-B2
Application number	US-201816167830-A
Country	US
Kind code	B2
Filing date	Oct 23, 2018
Priority date	Oct 30, 2017
Publication date	Mar 16, 2021
Grant date	Mar 16, 2021

Abstract

Preparation of halogen-doped silica is described. The preparation includes doping silica with high halogen concentration and sintering halogen-doped silica to a closed-pore state. The sintering includes a high pressure sintering treatment and a low pressure sintering treatment. The high pressure sintering treatment is conducted in the presence of a high partial pressure of a gas-phase halogen doping precursor and densifies a silica soot body to a partially consolidated state. The low pressure sintering treatment is conducted in the presence of a low partial pressure of gas-phase halogen doping precursor and transforms a partially consolidated silica body to a closed-pore state. The product halogen-doped silica glass exhibits little foaming when heated to form fibers in a draw process or core canes in a redraw process.

First claim

What is claimed is:

1. A method of producing halogen-doped silica comprising:
doping a silica soot body with a gas-phase doping precursor to form a doped silica soot body, the doped silica soot body having a density in the range from 0.25 g/cm 3 and 1.00 g/cm 3 , the gas-phase doping precursor comprising a halogen and having a partial pressure of at least 2.0 atm; and
sintering the doped silica soot body to a closed-pore state, the sintering comprising:
a first sintering treatment, the first sintering treatment transforming the doped silica soot body to a partially consolidated silica soot body in the presence of the gas-phase doping precursor, the gas-phase doping precursor having a partial pressure of at least 2.0 atm during the first sintering treatment, the partially consolidated silica soot body having a density less than 1.90 g/cm 3 and at least 0.15 g/cm 3 greater than the density of the doped silica soot body; and
a second sintering treatment, the second sintering treatment transforming the partially consolidated silica soot body to a closed-pore silica body, the closed-pore silica body having a density of at least 1.90 g/cm 3 and at least 0.05 g/cm 3 greater than the density of the partially consolidated silica soot body, the second sintering treatment occurring in a gas environment having a total pressure less than 1.0 atm.

2. The method of claim 1 , wherein the doped silica soot body has a density in the range from 0.45 g/cm 3 and 0.80 g/cm 3 .

3. The method of claim 1 , wherein the halogen comprises Cl or Br.

4. The method of claim 1 , wherein the gas-phase doping precursor comprises SiCl 4 or SiBr 4 .

5. The method of claim 1 , wherein the doping comprises a gas-phase doping precursor having a partial pressure of at least 10.0 atm.

6. The method of claim 1 , wherein the doping occurs at a temperature in the range from 1000° C.-1500° C.

7. The method of claim 1 , wherein the partially consolidated silica soot body has a density in the range from 1.20 g/cm 3 -1.80 g/cm 3 .

8. The method of claim 1 , wherein the partially consolidated silica soot body has a density at least 0.55 g/cm 3 greater than the density of the doped silica soot body.

9. The method of claim 1 , wherein the partially consolidated soot body includes an annular region of thickness 1 mm extending from the outermost radial position toward the center, the annular region having a density less than 1.7 g/cm 3 .

10. The method of claim 1 , wherein the first sintering treatment comprises a gas-phase doping precursor having a partial pressure of at least 5.0 atm.

11. The method of claim 1 , wherein the first sintering treatment occurs at a temperature in the range from 1000° C.-1500° C.

12. The method of claim 1 , wherein the first sintering treatment occurs in the presence of a diluent gas selected from the group consisting of He, Ne, Ar, Kr, Xe, O 2 , SO 2 , N 2 , CO and CO 2 .

13. The method of claim 1 , wherein the closed-pore silica body has a density of at least 2.00 g/cm 3 .

14. The method of claim 1 , wherein the closed-pore silica body has a density at least 0.15 g/cm 3 greater than the density of the partially consolidated silica soot body.

15. The method of claim 1 , wherein the second sintering treatment comprises a gas environment comprising a diluent gas selected from the group consisting of He, Ne, Ar, Kr, Xe, O 2 , SO 2 , N 2 , CO and CO 2 .

16. The method of claim 1 , wherein the second sintering treatment comprises a gas environment comprising the gas-phase doping precursor, the gas-phase doping precursor having a partial pressure less than 0.3 atm during the second sintering treatment.

17. The method of claim 1 , wherein the second sintering treatment comprises a gas environment having a total pressure less than 0.25 atm.

18. The method of claim 1 , wherein the second sintering treatment comprises a gas environment having a total pressure less than 0.01 atm.

19. The method of claim 1 , wherein the concentration of the halogen in the closed-pore silica body is greater than 2.0 wt %.

20. The method of claim 1 , wherein the concentration of the halogen in the closed-pore silica body is greater than 5.0 wt %.

Assignees

• Corning Inc

Inventors

• Bookbinder Dana Craig
• Dawes Steven Bruce
• Fiacco Richard Michael
• Harper Brian Lee
• Li Ming-Jun
• Tandon Pushkar

Classifications

• C03B37/01446 Primary

  Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering (C03B37/01853 takes precedence) · CPC title

• C03B2201/14

  doped with boron and fluorine · CPC title

• C03B2201/08

  doped with boron or fluorine or other refractive index decreasing dopant · CPC title

• C03B2201/12

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

• C03B19/1461

  for doping the shaped article with flourine · CPC title