Fiber optic transducer with fluid coupling means between optical fiber and transduction material

• US 5,491,335 A
• Filed: 08/31/1994
• Issued: 02/13/1996
• Est. Priority Date: 08/31/1994
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: McVicker, James A., Bucholtz, Frank
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): Steady, Jacqueline M.
• Application Number:
  US08/298,698
• Time in Patent Office: 531 Days
• Field of Search: 250/227.27, 250/227.25, 250/227.24, 385/12, 385/39, 385/48, 385/50
• US Class Current: 250/227.25
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G01R 33/0327 with application of magnetostriction

Abstract

A fiber optic transducer includes a fiber optic cable or ribbon, a sensor, fluid material for coupling the fiber optic medium to the sensor and an affixing material to optionally affix the position of the sensor position relative to the fiber optic ribbon by affixing only one end of the sensor to the fiber optic ribbon. The sensor can be made from either magnetostrictive or electrostrictive materials. The coupling fluid enables the transducers to be manufactured with substantially similar frequency responses across a range of frequencies.

Claims

1. A fiber optic transducer comprising:

an optical fiber;

a nonlinear transduction material in which strain resulting from an applied field is a nonlinear function of the applied field; and

fluid means disposed between said optical fiber and said nonlinear transduction material and having the capability of coupling alternating mechanical strain from said nonlinear transduction material to said optical fiber while simultaneously rejecting static mechanical strain.

2. The fiber optic transducer of claim 1 wherein:

said optical fiber is a fiber optic ribbon;

said nonlinear transduction material is in the form of a flat strip;

said fluid means is provided between said fiber optic ribbon and said flat strip .

3. The fiber optic transducer of claim 2 further including:

means for affixing a first end of said nonlinear transduction material to said fiber optic ribbon.

4. The fiber optic transducer of claim 3 wherein:

said affixing means is an epoxy adhesive.

5. The fiber optic transducer of claim 1 wherein:

said nonlinear transduction material is in the form of an annular jacket, said annular jacket having an interior wall and being coupled to said optical fiber by said fluid means, said annular sensor jacket being positioned around a portion of said optical fiber, said fluid means being provided between said optical fiber and said interior wall of said annular jacket.

6. The fiber optic transducer of claim 5 further including:

means for affixing a first end of said annular jacket to said optical fiber.

7. The fiber optic transducer of claim 6 wherein:

said affixing means is an epoxy adhesive.

8. The fiber optic transducer of claim 1 wherein:

said fluid means is a silicone vacuum grease.

9. The fiber optic transducer of claim 1 further including:

means for affixing a first end of said nonlinear transduction material to said optical fiber.

10. The fiber optic transducer of claim 9 wherein:

said affixing means is an epoxy adhesive.

11. The fiber optic transducer of claim 1 wherein:

said nonlinear transduction material is a magnetostrictive material.

12. The fiber optic transducer of claim 1 wherein:

said nonlinear transduction material comprises an annular mandrel having an exterior surface, said optical fiber being coiled around said exterior surface of said annular mandrel, and said fluid means provided between said exterior surface of said annular mandrel and said optical fiber.

19. The fiber optic transducer of claim 1 wherein:

said fluid means is selected from the group consisting of polydimethylsiloxane, trimethylsiloxy terminated, heavy mineral oil, motor oil and household oil.

20. The fiber optic transducer of claim 2 wherein:

said nonlinear transduction material is a magnetostrictive material.

21. The fiber optic transducer of claim 2 wherein:

said nonlinear transduction material is an electrostrictive material.

22. The fiber optic transducer of claim 2 wherein:

said fluid means is a silicone vacuum grease.

23. The fiber optic transducer of claim 2 wherein:

said fluid means is selected from the group consisting of polydimethylsiloxane, trimethylsiloxy terminated, heavy mineral oil, motor oil and household oil.

24. The fiber optic transducer of claim 5 wherein:

said nonlinear transduction material is a magnetostrictive material.

25. The fiber optic transducer of claim 5 wherein:

said nonlinear transduction material is an electrostrictive material.

26. The fiber optic transducer of claim 5 wherein:

said fluid means is a silicone vacuum grease.

27. The fiber optic transducer of claim 5 wherein:

said fluid means is selected from the group consisting of polydimethylsiloxane, trimethylsiloxy terminated, heavy mineral oil, motor oil and household oil.

28. The fiber optic transducer of claim 1 wherein:

said nonlinear transduction material is an electrostrictive material.

29. The fiber optic transducer of claim 12 wherein:

said nonlinear transduction material is a magnetostrictive material.

30. The fiber optic transducer of claim 12 wherein:

said nonlinear transduction material is an electrostrictive material.

31. The fiber optic transducer of claim 12 wherein:

said fluid means is a silicone vacuum grease.

32. The fiber optic transducer of claim 12 wherein:

said fluid means is selected from the group consisting of polydimethylsiloxane, trimethylsiloxy terminated, heavy mineral oil, motor oil and household oil.

13. A method for manufacturing a fiber optic transducer comprising the steps of:

providing an optical fiber;

providing a nonlinear transduction material in which strain resulting from an applied field is a nonlinear function of the applied field; and

providing between the optical fiber and the nonlinear transduction material a fluid having the capability of coupling alternating mechanical strain from the nonlinear transduction material to the optical fiber while simultaneously rejecting static mechanical strain.

14. The method of claim 13 further including the step of:

affixing a first end of the nonlinear transduction material to the optical fiber.

15. The method of claim 14 wherein said affixing step includes the step of:

using an epoxy adhesive to affix the first end of the nonlinear transduction material to the optical fiber.

16. A field detection device for detecting a strength of an external signal field, the device comprising:

means for generating an applied carrier field;

a fiber optic transducer comprising;

a nonlinear transduction material being responsive to the external signal field and the applied field for developing an induced strain therein;

an optical fiber; and

fluid means disposed between said optical fiber and said nonlinear transduction material for coupling said nonlinear transduction material to said optical fiber, said fluid means transferring the induced strain in said nonlinear transduction material into said optical fiber;

a light source;

an interferometer incorporating said fiber optic transducer as a sensor arm and receiving light from said light source, said light source sending light through said sensor arm, said sensor arm generating a total parameter shift in the light corresponding to the external signal field and the applied field; and

signal detecting means for converting the parameter shift in the light into a parameter shift signal, for extracting an external component signal from the parameter shift signal, the external component signal representative of the external signal field, and for converting the external component signal into a measurement signal corresponding to the external signal field.

17. The field detection device of claim 16 further including:

means for affixing a first end of said nonlinear transduction material to said optical fiber.

18. The field detection device of claim 17 wherein:

said affixing means is an epoxy adhesive.