Method for fabricating an optical fibre preform

Patent metadata

Field	Value
Publication number	US-11964899-B2
Application number	US-201816628423-A
Country	US
Kind code	B2
Filing date	Jul 4, 2018
Priority date	Jul 5, 2017
Publication date	Apr 23, 2024
Grant date	Apr 23, 2024

Abstract

A method of making an optical fibre preform comprising providing a hollow outer tube of glass, providing a hollow primary capillary tube of glass with an outer diameter smaller than an inner diameter of the outer tube, positioning the primary capillary tube inside the outer tube such that an outer surface of the primary capillary tube lies against an inner surface of the outer tube along a contact line parallel to the longitudinal axes of the primary capillary tube and the outer tube, and bonding the primary capillary tube into its position inside the outer tube by directing a laser beam onto a surface of the outer tube or the primary capillary at one or more locations aligned with the contact line.

First claim

The invention claimed is:

1. A method of making an optical fibre preform comprising:
providing a hollow outer tube of glass;
providing a hollow primary capillary tube of glass with an outer diameter smaller than an inner diameter of the outer tube;
positioning the primary capillary tube inside the outer tube such that an outer surface of the primary capillary tube lies against an inner surface of the outer tube along a contact line parallel to the longitudinal axes of the primary capillary tube and the outer tube;
placing one of a pair of magnetically attracted elements inside the primary capillary tube;
arranging a second of the pair of magnetically attracted elements outside the outer tube radially aligned with the contact line such that magnetic force between the pair of magnetically attracted elements pulls the capillary tube; and
bonding the primary capillary tube into its position inside the outer tube by directing a laser beam to be incident onto an outer surface of the outer tube or an inner surface of the primary capillary tube at one or more locations aligned with the contact line.

2. The method according to claim 1 , in which the laser beam deposits heat energy to cause softening of the glass of at least the outer tube or the primary capillary tube to enable the bonding.

3. The method according to claim 2 , in which the laser beam undergoes linear optical absorption in the glass.

4. The method according to claim 2 , in which the laser beam undergoes nonlinear optical absorption in the glass.

5. The method according to claim 1 , in which the laser beam undergoes nonlinear optical absorption in the glass to generate photo-ionisation to enable the bonding.

6. The method according to claim 1 , further comprising:
providing a hollow secondary capillary tube of glass with an outer diameter smaller than an inner diameter of the primary capillary tube; and,
before directing the laser beam, positioning the secondary capillary tube inside the primary capillary tube such that an outer surface of the secondary capillary tube lies against an inner surface of the primary capillary tube in radial alignment with the said contact line; wherein
directing the laser beam so as to bond both the primary capillary tube and the secondary capillary tube into their positions.

7. The method according to claim 1 , further comprising:
after directing the laser beam, positioning a further primary capillary tube inside the outer tube along a further contact line angularly spaced from the said contact line so that the primary capillary tube and the further primary capillary tube are spaced apart from one another,
optionally positioning a further secondary capillary tube inside the further primary capillary tube in radial alignment with the further contact line; and
directing the laser beam so as to bond the further primary capillary tube and if included, the further secondary capillary tube, into position.

8. The method according to claim 1 , in which:
the positioning comprises inserting the primary capillary tube into the outer tube and optionally the secondary capillary tube into the primary capillary tube, and supporting the outer tube in a horizontal orientation so that the capillary tube or tubes orient themselves at a lowest point inside the outer tube under gravity.

9. The method according to claim 8 , wherein the second of the pair of magnetically attracted element is positioned vertically below the outer tube.

10. The method according to claim 1 , further comprising:
holding the outer tube with a rotational stage; and
after the step of directing the laser beam, rotating the outer tube about its longitudinal axis to align a next contact line with the laser beam before performing a further positioning and a further directing of the laser beam with respect to the next contact line.

11. The method according to claim 1 , in which:
the positioning comprises inserting the primary capillary tube into the outer tube and optionally the secondary capillary tube into the primary capillary tube, and supporting an innermost of the capillary tubes in a horizontal orientation so that the remaining tube or tubes hang from the innermost tube under gravity.

12. The method according to claim 1 , in which:
the positioning includes the application of packing material to support the capillary tube or tubes in position during the directing of the focussed laser beam.

13. The method according to claim 1 , in which directing the laser beam comprises directing the laser beam onto the outer surface of the outer tube.

14. The method according to claim 1 , in which directing the laser beam comprises directing the laser beam onto the inner surface of the capillary tube.

15. The method according to claim 14 , comprising directing the laser beam longitudinally inside the outer tube to an optical directing element inside the outer tube which is configured to divert the beam towards a contact point.

16. The method according to claim 1 , in which directing the laser beam at one or more locations aligned with the contact line comprises directing the laser beam at two or more discrete locations spaced apart along the contact line.

17. The method according to claim 1 , in which directing the laser beam at one or more locations aligned with the contact line comprises directing the laser beam continuously along the contact line.

18. The method according to claim 16 , comprising using a translation stage to provide relative linear motion parallel to the contact line between the outer tube and the laser beam to position the laser beam for directing of the laser beam at the one or more locations.

19. The method according to claim 1 , further comprising:
providing an additional hollow outer tube of glass with an inner diameter larger than an outer diameter of the said outer tube;
positioning the said outer tube inside the additional outer tube such that an outer surface of the said outer tube lies against an inner surface of the additional outer tube along a further contact line being the said contact line; and
directing the laser beam onto a surface of the additional outer tube or the said outer tube at one or more locations aligned with the further contact line so as to bond the outer tube into its position inside the additional outer tube.

20. The method according to claim 1 , in which directing the laser beam comprises focussing the laser beam and positioning the focus to coincide with the contact line.

21. The method according to claim 1 , comprising directing the laser beam in radial alignment with the contact line.

22. The method according to claim 1 , comprising directing the laser beam angularly spaced from radial alignment with the contact line.

23. The method according to claim 1 , comprising directing a second laser beam at or adjacent to the one or more locations simultaneously with directing the said laser beam.

24. The method according to claim 1 , in which the glass of the hollow outer tube and the glass of the primary capillary tube comprises silica, and the laser beam has a wavelength of 10.6 μm.

25. A method of fabricating a hollow core optical fibre or a cane for a hollow core optical fibre, comprising:
fabricating an optical fibre preform according to the method of claim 1 ; and
drawing the preform under the application of heat to a required diameter for the optical fibre or the cane.

26. A method of mak

Assignees

• Univ Southampton

Inventors

• Wheeler Natalie
• Shardlow Peter
• Poletti Francesco

Classifications

• C03B37/0122 Primary

  for making preforms of photonic crystal, microstructured or holey optical fibres · CPC title

• C03B23/207 Primary

  Uniting glass rods, glass tubes, or hollow glassware (C03B23/24 takes precedence) · CPC title

• C03B37/01225

  Means for changing or stabilising the shape, e.g. diameter, of tubes or rods in general, e.g. collapsing · CPC title

• G02B6/02328

  Hollow or gas filled core · CPC title

• C03B2203/16

  Hollow core · CPC title