High-temperature-resistant Bragg grating optical fibre sensor and method for manufacturing same

Patent metadata

Field	Value
Publication number	US-11709078-B2
Application number	US-201917284196-A
Country	US
Kind code	B2
Filing date	Oct 11, 2019
Priority date	Oct 12, 2018
Publication date	Jul 25, 2023
Grant date	Jul 25, 2023

Abstract

A Bragg grating optical fiber sensor for measuring temperatures and deformations and a method for manufacturing same, the manufacturing method including ablating a mechanical coating over a portion of an optical fiber so as to form an opening extending radially over the entire thickness of the mechanical coating, and inscribing a Bragg grating into the optical fiber through the opening.

First claim

The invention claimed is:

1. A Bragg grating optical fibre sensor, comprising:
an optical fibre including a core;
an optical cladding surrounding the core; and
a mechanical coating surrounding the optical cladding, wherein
the mechanical coating includes a metal and an opening arranged to enable patterns of a Bragg grating to be inscribed by passing a laser beam through said opening, the opening extending radially over an entire thickness thereof, and
the optical fibre includes the Bragg grating inscribed in the core at the opening.

2. The optical fibre sensor of claim 1 , wherein the opening extends circumferentially over an angular sector defined so that the opening has, by projection in a plane parallel to a longitudinal axis of the optical fibre, a width greater than or equal to a corresponding dimension of the patterns of the Bragg grating.

3. The optical fibre sensor of claim 1 , wherein the opening extends circumferentially over an angular sector defined so that the opening has, by projection in a plane parallel to a longitudinal axis of the optical fibre, a width greater than or equal to a diameter of the core of the optical fibre.

4. The optical fibre sensor of claim 1 , wherein the opening extends circumferentially over an angular sector of between 0.5 degrees and 120 degrees.

5. The optical fibre sensor of claim 1 , wherein the Bragg grating extends longitudinally over a sensitive portion of the optical fibre and the opening extends longitudinally over a cutout portion of the optical fibre, a length of the cutout portion being greater than or equal to a length of the sensitive portion.

6. The optical fibre sensor of claim 1 , wherein the mechanical coating includes a plurality of openings, each opening being arranged to allow inscription of the patterns of the Bragg grating by passing a laser beam through said opening and extending radially over the entire thickness of the mechanical coating, the optical fibre including a plurality of Bragg gratings, each Bragg grating being inscribed in the core at one of the openings.

7. The optical fibre sensor of claim 1 , wherein the mechanical coating comprises a material the pyroscopic resistance of which is greater than or equal to 800° C.

8. The optical fibre sensor of claim 1 , wherein the mechanical coating consists of one or more metals.

9. The optical fibre sensor of claim 1 , wherein the mechanical coating has a thickness of between 10 micrometres and 500 micrometres.

10. A method for manufacturing a Bragg grating optical fibre sensor from an optical fibre including a core, an optical cladding surrounding the core, and a mechanical coating surrounding the optical cladding, the mechanical coating comprising a metal, the method comprising:
ablating the mechanical coating over a cutout portion of the optical fibre so as to form an opening extending radially over an entire thickness of the mechanical coating; and
inscribing a Bragg grating in the optical fibre through the opening, wherein
the ablating comprises an insolation of the mechanical coating by a laser beam focused in a vicinity of the mechanical coating, the laser beam being formed by femtosecond pulses.

11. The method of claim 10 , wherein the ablating comprises circumferentially extending the opening over an angular sector defined so that the opening has, by projection in a plane parallel to a longitudinal axis of the optical fibre, a width greater than or equal to a corresponding dimension of patterns of the Bragg grating.

12. The method of claim 10 , wherein the ablating comprises circumferentially extending the opening over an angular sector defined so that the opening has, by projection in a plane parallel to a longitudinal axis of the optical fibre, a width greater than or equal to a diameter of the core of the optical fibre.

13. The method of claim 10 , wherein the ablating comprises circumferentially extending the opening over an angular sector of between 0.5 degrees and 120 degrees.

14. The method of claim 10 , wherein the ablating comprises sweeping the laser beam over the mechanical coating.

15. The method of claim 10 , wherein the ablating comprises an insolation of a portion on the mechanical coating corresponding to the opening by a plurality of pulses.

16. The method of claim 10 , wherein each pulse of the laser beam has an energy fluence greater than or equal to a threshold of energy fluence of ablation of the mechanical coating and less than or equal to a threshold of energy fluence of ablation of the optical cladding.

17. The method of claim 10 , wherein a focal point of the laser beam is positioned upstream of the mechanical coating.

18. The method of claim 10 , wherein the inscribing of the Bragg grating comprises an insolation of the core of the optical fibre by an ultraviolet laser beam, the core of the optical fibre being photosensitive.

19. The method of claim 10 , wherein the inscribing of the Bragg grating comprises an insolation of the core of the optical fibre by a femtosecond laser beam pulse.

20. The method of claim 10 , wherein the mechanical coating comprises a material the pyroscopic resistance of which is greater than or equal to 800° C.

Assignees

• Commissariat Energie Atomique

Inventors

• Desmarchelier Rudy
• Laffont Guillaume

Classifications

• G01D5/35316 Primary

  using a Bragg gratings · CPC title

• G02B6/02147

  Point by point fabrication, i.e. grating elements induced one step at a time along the fibre, e.g. by scanning a laser beam, arc discharge scanning (G02B6/02133 and G02B6/02142 take precedence) · CPC title

• G02B6/02395

  Glass optical fibre with a protective coating, e.g. two layer polymer coating deposited directly on a silica cladding surface during fibre manufacture (G02B6/02052, G02B6/02057, G02B6/024, G02B6/032, G02B6/105, G02B6/14 take precedence; coating on fibre gratings G02B6/02104; multilayer core or cladding G02B6/036; reinforcing splice joints G02B6/2558; optical cables, i.e. comprising protective structures external to the protective coating such as a jacket or plural coated optical fibres G02B6/44; coating of glass to obtain optical fibres C03C25/104) · CPC title