Fiber Bragg grating (FBG) sensor

Patent metadata

Field	Value
Publication number	US-9335482-B2
Application number	US-201214115507-A
Country	US
Kind code	B2
Filing date	May 4, 2012
Priority date	May 4, 2011
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A fiber Bragg grating (FBG) sensor structure, a method of fabricating a FBG sensor structure, and a method of employing a FBG sensor structure comprising an optical fiber portion having at least one FBG formed therein. The FBG sensor structure comprises an optical fiber portion having at least one FBG formed therein; and a sleeve structure capable of transferring vibrations and/or strain along a length thereof; wherein the optical fiber portion is coupled to the sleeve structure such that the central wavelength of the FBG, is variable under the transferred vibrations and/or strain.

First claim

The invention claimed is:

1. A fiber Bragg grating (FBG) sensor structure comprising:
an optical fiber portion having at least one FBG formed therein between two ends of the optical fiber portion; and
a sleeve structure capable of transferring vibrations and/or strain along a length thereof, the sleeve structure comprising a resilient metallic cable;
wherein the optical fiber portion is coupled to the sleeve structure such that the wavelength of the optical fiber portion is variable in response to the change in wavelength experienced by the FBG under the transferred vibrations and/or strain,
wherein the optical fiber portion is disposed inside the sleeve structure and the optical fiber portion is coupled to an inner circumference of the sleeve structure,
wherein the optical fiber portion comprises two spaced collars located between the FBG and respective ends of the optical fiber portion, the collars connecting the optical fiber portion to the inner circumference of the sleeve structure, and
wherein the sensor structure is configured to be installed in a pre-tensioned state to increase sensitivity of the sensor.

2. The FBG sensor structure as claimed in claim 1 , wherein the optical fiber portion is coupled to the sleeve structure such that the wavelength of the optical fiber portion is variable under amplitude and frequency of the transferred vibrations and/or strain.

3. The FBG sensor structure as claimed in claim 1 , wherein the ends of the optical fiber portion are connected to the inner circumference of the sleeve structure.

4. The FBG sensor structure as claimed in claim 1 , wherein at least one of the two spaced collars is formed from epoxy.

5. The FBG sensor structure as claimed in claim 1 , wherein the resilient metallic cable comprises a resilient helical metallic tube.

6. The FBG sensor structure as claimed in claim 5 , wherein the resilient metallic cable further comprises a protective cover on the resilient helical metallic tube.

7. The FBG sensor structure as claimed in claim 6 , wherein the protective cover comprises a UV protection material.

8. The FBG sensor structure as claimed in claim 1 , further comprising a buffered fiber portion connected to at least one end of the optical fiber portion.

9. The FBG sensor structure as claimed in claim 8 , wherein the buffered fiber portion extends along the length of the sleeve structure for optical connection of the optical fiber portion.

10. The FBG sensor structure as claimed claim 9 , wherein two buffered fiber portions are connected at respective ends of the optical fiber portion.

11. The FBG sensor structure as claimed in claim 1 , wherein the sleeve structure is configured for suspending the optical fiber portion at a sensing location.

12. The FBG sensor structure as claimed in claim 1 , wherein the optical fiber portion comprises a single fiber having an array of FBGs formed therein.

13. The FBG sensor structure as claimed in claim 1 , wherein the FBG sensor structure comprises a plurality of optically interconnected optical fiber portions having respective FBGs formed therein, each optical fiber portion coupled to the sleeve structure such that the central wavelength of each FBG is variable under the transferred vibrations and/or strain.

14. The FBG sensor structure as claimed in claim 1 , wherein the optical fiber portion comprises a single mode fiber.

15. The FBG sensor structure as claimed in claim 14 , wherein the optical fiber portion further comprises a loose sleeve disposed over the single mode fiber.

16. The FBG sensor structure as claimed in claim 1 , further comprising an interrogator optically connected to the one or more optical fiber portions, the interrogator configured to transmit signals to the one or more optical fiber portions, and measure signals reflected from the one or more optical fiber portions.

17. A method of fabricating a FBG sensor structure, the method comprising:
providing an optical fiber portion having two ends and at least one FBG formed between those ends; and
coupling the optical fiber portion to an inner circumference of a sleeve structure using two spaced collars located between the FBG and respective ends of the optical fiber portion, the sleeve structure being capable of transferring vibrations and/or strain along a length thereof and configured to be installed in a pre-tensioned state, the sleeve structure comprising a resilient metallic cable, such that the central wavelength of the FBG is variable under the transferred vibrations and/or strain.

18. The method as claimed in claim 17 , further comprising connecting the ends of the optical fiber portion to the inner circumference of the sleeve structure.

19. The method as claimed in claim 17 , further comprising forming the collars from epoxy.

20. The method as claimed in claim 17 , wherein one optical fiber portion and one sleeve structure forms one sensing element.

21. The method as claimed in claim 20 , further comprising connecting a plurality of sensing elements to forma sensor array.

22. The method as claimed in claim 17 , wherein the optical fiber portion has an array of FBGs formed therein.

23. The method as claimed in claim 17 , comprising fabricating a plurality of optically interconnected optical fiber portions, and feeding said plurality of interconnected optical fiber portions into a single sleeve structure to form a sensor array.

24. A method of employing a FBG sensor structure comprising an optical fiber portion having at least one FBG formed therein; the method comprising pre-tensioning the FBG sensor structure and detecting wavelength variations of the optical fiber portion in response to the change in wavelength experienced by the FBG under vibrations and/or strain transferred using a sleeve structure, the optical fiber portion being coupled to an inner circumference of the sleeve structure by two spaced collars located between the FBG and respective opposite ends of the optical fiber portion, the sleeve structure comprising a resilient metallic cable.

25. The method as claimed in claim 24 , further comprising suspending the FBG sensor structure between two substantially fixed mounting elements, such that the sleeve structure extends along a structural feature disposed between the mounting elements.

26. The method as claimed in claim 25 , wherein disturbances experienced by the structural feature are detected by the sleeve structure as vibrations and/or strain and transferred to the optical fiber portion, resulting in a variation of wavelength of the FBG.

27. The method as claimed in claim 25 , wherein the pre-tension of the FBG sensor structure results from the FBG structure being suspended in a pre-tensioned fashion.

28. The method as claimed in claim 25 , wherein the structural feature comprises a fence, and the mounting elements comprise of the fence near the struts of the fence.

29. The method as claimed in claim 25 , wherein the FBG sensor structure is fixed by way of metal plates connected to the mounting elements.

30. The method as claimed in claim 25 , wherein the FBG structure is supported in regions between the mounting elements in a manner such as to allow transfer of the vibrations and/or strain using the sleeve structure coupled to the optical fiber portion.

31. The method as claimed in claim 30 , wherein the FBG str

Assignees

• Hao Jianzhong
• Dong Bo
• Paulose Varghese
• Lin Bo
• Agency Science Tech & Res

Inventors

• Hao Jianzhong
• Dong Bo
• Paulose Varghese
• Lin Bo

Classifications

• G02B6/02209

  Mounting means, e.g. adhesives, casings (G02B6/02171 and G02B6/02195 take precedence) · CPC title

• G02B6/2558

  Reinforcement of splice joint · CPC title

• G02B6/34 Primary

  utilising prism or grating {(G02B6/293 takes precedence)} · CPC title

• G01L1/246 Primary

  using integrated gratings, e.g. Bragg gratings · CPC title

• G08B13/124

  with the breaking or disturbance being optically detected, e.g. optical fibers in the perimeter fence · CPC title