Soot Pressing for Optical Fiber Overcladding

• US 20110132038A1
• Filed: 12/02/2010
• Published: 06/09/2011
• Est. Priority Date: 12/03/2009
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Jennings, Douglas H., Kozlov, Valery A., Li, Ming-Jun, Dawes, Steven Bruce, Tandon, Pushkar, Wang, Ji, Filippov, Andrey V.
• Granted Patent: US 8,468,852 B2
• Time in Patent Office: Days
• US Class Current: 65/408
• CPC Class Codes: C03B 2203/04 Polygonal outer cross-section, e.g. triangular, square
• CPC Class Codes: C03B 2203/14 Non-solid, i.e. hollow products, e.g. hollow clad or with core-clad interface
• CPC Class Codes: C03B 2203/31 by use of stress-imparting rods, e.g. by insertion
• CPC Class Codes: C03B 2203/34 Plural core other than bundles, e.g. double core
• CPC Class Codes: C03B 2203/42 Photonic crystal fibres, e.g. fibres using the photonic bandgap PBG effect, microstructured or holey optical fibres
• CPC Class Codes: C03B 37/01282 by pressing or sintering, e.g. hot-pressing
• CPC Class Codes: Y02P 40/57 Improving the yield, e-g- reduction of reject rates

Abstract

A method and an apparatus for making an optical fiber preform comprising the steps of (i) depositing a plurality of rods are deposited into an inner cavity of an apparatus; (ii) depositing particulate glass material in the inner cavity between the rods and the inner wall; and (iii) applying pressure against the particulate glass material to pressurize the particulate glass material against the plurality of rods.

Claims

1. A method for making an optical fiber preform comprising the steps of:

depositing a plurality of rods into an mold cavity of an apparatus;

depositing particulate glass material in the mold cavity between the rods and the inner wall; and

applying pressure against the particulate glass material to pressurize the particulate glass material against the plurality of rods.

2. The method for making an optical fiber preform according to claim 1, wherein said plurality of rods comprising:

(i) at least one glass rod and at least one mold rod;

or (ii) at least two glass rods; and

said pressure is applied axially and/or radially.

3. The method for making an optical fiber preform according to claims 1, wherein said apparatus comprises an outer wall and an inner wall, the outer wall surrounding the inner wall and the inner wall surrounding the mold cavity;

and the pressure is applied at least radially inwards, and is 25 psig to 250 psig against the particulate glass material to pressurize the particulate glass material against the rods.

4. The method of claim 3 wherein the step of applying a radially inward pressure comprises providing a pressurized fluid between the outer wall and the inner wall.

5. The method of claims 1 comprising:

compressing the particulate glass material in an axial direction to form a soot compact having a density of at least 0.5 g/cc, wherein the soot compact is the cladding portion of the optical fiber preform assembly.

6. The method of claim 5, wherein said particulate glass material is silica soot, and wherein the silica glass soot is loaded by:

loading the mold cavity with a first portion of silica glass soot;

compacting the first portion of silica glass soot;

loading the mold cavity with a second portion of silica glass soot; and

compacting the second portion of silica glass soot.

7. The method of claim 1, wherein at least one of said rods is a consolidated glass rod.

8. The method of claim 1, wherein at least one at least one of said rods is a core cane situated along the axial center of said mold cavity

9. The method of claim 2, wherein at least one of the glass rods comprises a consolidated core cane surrounded by a porous soot clad layer and said core cane is situated along the axial center of said mold cavity.

10. The method of claim 2, wherein at lest one of said at least two glass rods is a consolidated B doped silica rod.

11. The method of claim 2, wherein prior to the step of applying a radial pressure against the particulate glass material, the particulate glass material has an average density of from 0.1 to 0.5 grams per cubic centimeter.

12. The method of claim 1, wherein the particulate glass material is waste soot from a CVD deposition operation.

13. The method of claim 2, wherein subsequent to the step of applying a radial pressure against the particulate glass material, the pressurized particulate glass material has a density of from 0.6 to 1.2 grams per cubic centimeter.

14. The method of claim 1, wherein during the step of applying pressure against the particulate glass material, the temperature of the inner cavity is less than 50°

C.

15. The method of claim 4, wherein the pressurized fluid is air.

16. The method of claim 3, wherein the inner wall comprises a flexible material having a tensile strength of 95 to 7,000 psi and an elongation of 200% to 800%.

17. The method of claim 3, wherein the inner wall comprises a toroidal bladder.

18. The method of claim 3, wherein the inner wall comprises a rolled sheet with interdigitated fingers and the step of applying a radially inward pressure comprises pulling the interdigitated fingers in opposite directions in order to reduce the diameter of the rolled sheet.

19. The method of claim 1, wherein the preform has a largest and smallest diameter along its axial length, wherein the smallest diameter is at least 90% of the largest diameter.

20. The method of claim 1, wherein the pressure is from 50 psig to 200 psig.

21. The method of claim 1, wherein subsequent to the step of applying a pressure against the particulate glass material, the pressurized particulate glass has a density of from 0.8 to 1.0 grams per cubic centimeter.

22. An optical fiber preform made in accordance with the method of claim 1, wherein the particulate glass material is pressurized against the rods and has a density of from 0.6 to 1.2 grams per cubic centimeter and wherein the preform has a largest and smallest diameter along its axial length, wherein the smallest diameter is at least 90% of the largest diameter.

23. The optical fiber preform of claim 22, wherein the smallest diameter is at least 95% of the largest diameter.

24. The method of claim 2 further comprising applying vibratory energy to the mold cavity as the silica glass soot is compressed.

25. The method of claim 24 wherein the vibratory energy comprises multiple frequency modes and the multiple frequency modes are swept over a range of frequencies.

26. The method of claim 6, further comprising applying vibratory energy to the mold body as the first portion of silica glass soot and the second portion of silica glass soot are loaded into the mold cavity.

27. The method of claim 1 further comprising:

pre-sintering the soot compact; and

machining the soot compact after pre-sintering.

28. The method of claim 1, wherein said rods are multiple core canes.

29. The method of claim 1 wherein said rods are arranged co-linearly within the mold cavity.

30. The method of claim 28 wherein said core canes are arranged co-linearly within the mold cavity.

31. The method of claim 28 wherein the pressure is applied to one or more sides of the mold cavity.

32. The method of claim 28 wherein the mold cavity does not have circular symmetry.