Fiber anchoring method for optical sensors

• US 20060285813A1
• Filed: 06/12/2006
• Published: 12/21/2006
• Est. Priority Date: 06/10/2005
• Status: Abandoned Application

• Current Assignee: Micron Optics Incorporated (Luna Innovations, Inc.)
• Original Assignee: Micron Optics Incorporated (Luna Innovations, Inc.)
• Inventors: Ferguson, Stephen K.
• Application Number:
  US11/452,094
• Publication Number:
  US 20060285813A1
• Time in Patent Office: Days
• US Class Current: 385/138
• CPC Class Codes: G01B 11/16 for measuring the deformation in a solid, e.g. optical strain gauge
• CPC Class Codes: G01D 11/245 Housings for sensors
• CPC Class Codes: G01D 5/353 influencing the transmission properties of an optical fibre
• CPC Class Codes: G01K 15/00 Testing or calibrating of thermometers
• CPC Class Codes: G01K 15/007 Testing
• CPC Class Codes: G02B 6/0218 using mounting means, e.g. by using a combination of materials having different thermal expansion coefficients
• CPC Class Codes: G02B 6/022 using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper G02B6/02204 takes precedence; optical modulation using photo-elastic effect G02F1/0131
• CPC Class Codes: G02B 6/02209 Mounting means, e.g. adhesives, casings G02B6/02171 and G02B6/02195 take precedence

Abstract

The invention relates generally to optical sensors that impart physical strain to an optical fiber by varying the tension applied axially to the fiber, which causes a change in the optical property of the light transmitted through the fiber. Methods, devices and device components for optical sensors are provided. The invention provides fiber holders capable of retaining a fiber under tension with little or no creep even in high temperature, high humidity environments. An exemplary fiber holder of the present invention provides superior retaining properties over epoxy and other adhesives while preserving the tensile strength of the original fiber. The invention further provides fiber holders and sensors, which are particularly useful for monitoring ambient conditions and measuring physical properties and mechanical phenomena.

Claims

1. An optical fiber retaining device comprising:

a fiber holder having a bore or slot extending along the longitudinal axis of the fiber holder;

an optical fiber that passes through the bore or slot in the fiber holder and which is oriented parallel to longitudinal axis of the fiber holder; and

a glass or metal seal formed between the optical fiber and the holder which is formed at least partially within the bore or slot of the fiber holder.

2. The device of claim 1 wherein the seal is a glass seal.

3. The device of claim 1 wherein the optical fiber has a protective coating.

4. The optical fiber retaining method of claim 1 wherein the seal between optical fiber and the fiber holder is formed over the protective coating of the fiber.

5. The optical fiber retaining device of claim 1 wherein the optical fiber has a protective coating that is not removed during the sealing process.

6. The optical fiber retaining device of claim 2 wherein the glass seal material has a coefficient of thermal expansion greater than that of the optical fiber.

7. The optical fiber retaining device of claim 2 wherein the fiber holder material has a coefficient of thermal expansion greater than that of the glass seal material.

8. The optical fiber retaining device of claim 2 wherein a compression seal is formed.

9. The optical fiber retaining device of claim 2 wherein the fiber holder material has a coefficient of thermal expansion substantially matched to that of the glass seal material.

10. The optical fiber retaining device of claim 1 wherein the fiber holder is fabricated from stainless steel, Kovar, or Invar.

11. The optical fiber retaining device of claim 1 wherein the fiber holder has a seal-retaining cavity at least in part formed in the bore or slot of the holder.

12. The optical fiber retaining device of claim 1 wherein the fiber has a polyimide protective coating made of polyimide, carbon-polyimide, or carbon-Silicone-PFA.

13. The optical fiber retaining device of claim 1 wherein the fiber has a metallic protective coating made of gold, copper, or aluminum.

14. The optical fiber retaining device of claim 13 wherein the sealing material is a metal alloy.

15. The optical fiber retaining device of claim 14 wherein the sealing material is a metal alloy solder comprising lead, tin, silver, Indium, gold, or copper.

16. The optical fiber retaining device of claim 1 further comprising a second fiber holder having an bore or slot extending along the longitudinal axis of the fiber holder;

wherein the optical fiber with protective coating passes through the bore or slot in the second fiber holder and is oriented parallel to the longitudinal axis of the second fiber holder; and

a second glass or metal seal formed around the optical fiber and at least partially within bore or slot of the fiber holder forming a seal between the coated optical fiber and the second fiber holder wherein the first and second fiber holders are spaced apart along the optical fiber forming two anchor points along the fiber.

17. The optical fiber retaining device of claim 16 further comprising one or more additional fiber holders each having a bore or slot extending along the longitudinal axis of the fiber holder;

wherein the optical fiber with protective coating passes through the bore or slot of each additional fiber holder and is oriented parallel to the longitudinal axes of each additional fiber holder; and

for each additional fiber holder an additional glass or metal seal for each additional fiber holder formed around the optical fiber and at least partially within the bore or slot of the additional fiber holder forming a seal between the coated optical fiber and each of the additional fiber holders wherein the fiber holders are spaced apart along the optical fiber forming a plurality of anchor points along the optical fiber.

18. The optical fiber retaining device of claim 16 wherein the fiber contains a Bragg grating located between the two anchor points.

19. The optical fiber retaining device of claim 17 wherein the fiber contains a Bragg grating between one or more anchor points.

20. The fiber retaining device of claim 16 wherein the fiber contains a Long Period Grating located between the two anchor points.

21. An optical sensor comprising a fiber retaining device of claim 16 and further comprising a fixture that holds first fiber holder and second fiber holder with their axial bores aligned, wherein at least a portion of said fixture is elastic with respect to expansion, compression or both along the longitudinal axis;

and wherein one or more optical properties of the optical fiber varies when subjected to axial strain.

22. The optical sensor of claim 21 wherein the seals are glass seals.

23. The optical sensor of claim 21 wherein the seals are formed from metal alloy solder.

24. The optical sensor of claim 21 which is a device for measuring strain.

25. The optical sensor of claim 21 which is a device for measuring displacement.

26. The optical sensor of claim 21 which is a device for measuring temperature.

27. The optical sensor of claim 21 which is a device for measuring pressure.

28. The optical sensor of claim 21 which is a device for measuring acceleration.

29. A method for measuring strain in an optical fiber which employs the optical sensor of claim 21.

30. A method for mounting a optical fiber having a protective coating in a fiber holder which comprises the step of providing a glass or metal seal between the fiber holder and the coated optical fiber.

31. The method of claim 30 wherein the glass or metal seal is formed within a seal-retaining cavity formed at least in part within a bore or slot in the fiber holder.

32. The method of claim 31 wherein the optical fiber extends entirely through the bore or slot of the fiber holder.