Two step etching process for an optical fiber preform

• US 6,821,449 B2
• Filed: 12/12/2002
• Issued: 11/23/2004
• Est. Priority Date: 12/14/2001
• Status: Expired due to Fees

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Koh, Joohyun, Caplen, Julie E., deSandro, Jean-Philippe J.
• Primary Examiner(s): OLSEN, ALLAN W
• Application Number:
  US10/319,044
• Publication Number:
  US 20030150242A1
• Time in Patent Office: 712 Days
• Field of Search: 216/24, 216/80, 654/28, 654/29
• US Class Current: 216/24
• CPC Class Codes: C03B 2201/31 doped with germanium
• CPC Class Codes: C03B 37/01466 Means for changing or stabilising the diameter or form of tubes or rods C03B37/01861 takes precedence
• CPC Class Codes: C03B 37/01861 Means for changing or stabilising the diameter or form of tubes or rods
• CPC Class Codes: C03C 25/68 by etching
• CPC Class Codes: Y02P 40/57 Improving the yield, e-g- reduction of reject rates

Abstract

This invention relates to a method of preparing an optical fiber preform with the preform having a uniform refractive index profile for the deposited oxide material that ultimately forms the optical fiber core. One embodiment of the invention relates to a process for preparing an optical fiber preform comprising the steps of etching a substrate a first time to remove a portion of a deposited oxide material from the preform by using a gas comprising an etchant gas containing fluorine at a sufficient temperature and gas concentration to create a fluorine contamination layer in the remaining deposited oxide material; and etching the preform a second time using a gas comprising an etchant gas containing fluorine at a sufficient temperature and gas concentration to remove the fluorine contamination layer without any substantial further fluorine contamination of the remaining deposited oxide material. Further embodiments relate to similar processes.

Claims

1. A process for preparing an optical fiber preform comprising the steps of:

a) etching an optical fiber preform a first time to remove a portion of an oxide material deposited on the preform by using a gas comprising a first etchant gas containing fluorine at a sufficient temperature and gas concentration to create a fluorine contamination layer in the remaining oxide material; and

b) etching the preform a second time using a gas comprising a second etchant gas containing fluorine at a sufficient temperature and gas concentration to remove the fluorine contamination layer without any substantial further fluorine contamination of the remaining deposited oxide material.

2. The process in claim 1, wherein the deposited oxide material is vitreous.

3. The process in claim 2, wherein the preform is a partially collapsed prior to etching, the preform having an inner and outer surface and the deposited oxide material forms the inner surface.

4. The process in claim 3, wherein the preform is partially collapsed before etching and has an inner diameter of less than about 10 mm.

5. The process in claim 3, wherein the temperature in the first etch step is less than about 1700°

C.

6. The process in claim 5, wherein the temperature in the second etch step is greater than about 1650°

C.

7. The process in claim 6, wherein the temperature in the first etch step is less than 1600°

C.

8. The process in claim 7, wherein the first etchant gas has a flow rate of greater than about 65 sccm.

9. The process in claim 8, wherein the first and second etchant gases are selected from the group consisting of CF₄, SF₆, NF₃, C₂F₆, C₄F₈, CHF₃, and combinations thereof.

10. The process in claim 8, wherein the first etchant gas is SF₆ and the second etchant gas is C₂F₆.

11. A process for preparing an optical fiber preform comprising the steps of:

a) partially collapsing a glass tube, with an inner and outer surface comprising at least one oxide material deposited on the inside of the tube, the oxide material comprising a dopant, under conditions which results in the depletion of some of the dopant out of the deposited oxide material for a distance from the inside surface;

b) etching the glass tube a first time to remove part or all of the dopant depleted layer from the deposited oxide material using a gas comprising a first etchant gas containing fluorine at a sufficient temperature and gas concentration to create a fluorine contamination layer in the remaining deposited oxide material; and

c) etching the partially collapsed glass tube a second time using a gas comprising a second etchant gas at a sufficient temperature and gas concentration to remove any remaining dopant depleted layer and at least a portion of the fluorine contamination layer.

12. The process in claim 11, wherein the deposited oxide material is vitreous.

13. The process in claim 12, wherein the partially collapsed glass tube has an inner diameter of less than about 5 mm.

14. The process in claim 12, wherein the temperature in the first etch step is at less than about 1700°

C.

15. The process in claim 14, wherein the temperature in the second etch step is at greater than about 1650°

C.

16. The process in claim 15, wherein the first and second etchant gases are selected from the group consisting of CF₄, SF₆, NF₃, C₂F₆, C₄F₈, CHF₃, and combinations thereof.

17. The process in claim 15, wherein the first etchant gas is SF₆ and the second etchant gas is C₂F₆.