Claims
- 1. A fiber optic sensor that includes a flexural disk having a pair of fiber optic coils mounted on opposite sides thereof and optically coupled together to form an interferometer that produces an output signal in response to acceleration of the flexural disk, comprising:
a housing having first and second end plates with a sidewall extending therebetween, the sidewall having an inwardly facing groove therein, the flexural disk having an outer edge portion mounted in the inward facing groove; and a compressive damper mounted in the housing and arranged to exert a compressive force on the flexural disk to control movement thereof in response to acceleration of the flexural disk along a sensing axis and thereby control the output signal amplitude over a selected operational frequency range.
- 2. The fiber optic sensor of claim 1 wherein the compressive damper comprises:
a first compressive damping member mounted between a first side of the flexural disk and the first end plate; and a second compressive damping member mounted between a second side of the flexural disk and the second end plate.
- 3. The fiber optic sensor of claim 2, further comprising a support member extending between oppositely facing portions of the first and second end plates, wherein each of the first and second compressive damping members comprises a cylinder formed of a viscoelastic material having a central passage therein, the first and second damping members being mounted in the housing such that the support member extends through the central passages in the first and second compressive damping members.
- 4. The fiber optic sensor of claim 1 wherein each of the end plates have ribbed inner surfaces with a plurality of ribs extending away from the end plates inward in the housing.
- 5. The fiber optic sensor of claim 4 wherein the ribs provide stiffening such that resonance of the housing is greater than the selected operational frequency range.
- 6. The fiber optic sensor of claim 5 wherein the ribbed inner surfaces of the end plates provide the housing with a mass that enables the fiber optic sensor to be neutrally buoyant in water.
- 7. The fiber optic sensor of claim 4 wherein the plurality of ribs are arranged to axially compress the compressive damper.
- 8. The fiber optic sensor of claim 4 wherein the ribs extend radially between the support member and the sidewall of the housing.
- 9. The fiber optic sensor of claim 4, further including an optical coupler connected to the first and second fiber optic coils and wherein an adjacent pair of ribs in the first end plate has slots formed therein for mounting the optical coupler in the housing.
- 10. The fiber optic sensor of claim 9, further comprising a plurality of routing tabs extending inward from the sidewall for retaining optical fibers in selected positions in the housing.
- 11. The fiber optic sensor of claim 3 wherein the flexural disk includes a central passage therethrough, the central support extending through the central passage in the flexural disk with an inner edge of the central passage in the flexural disk being spaced apart from the support member, further comprising a shear damper mounted on the central support member and arranged to exert a radial force on the inner edge of the flexural disk to dampen vibrations of the flexural member and thereby further control the output signal amplitude over a selected frequency range.
- 12. The fiber optic sensor of claim 11, wherein the support member is formed to have a pair of base portions connected to the first and second end plates, the shear damper being mounted at a central region of the support member between the base portions and being restrained against lengthwise motion relative to the support member.
- 13. The fiber optic sensor of claim 10 wherein the support member is formed to have a circumference that increases lengthwise away from the central region, the damping member comprising a length of tubing formed of a viscoelastic material, the damping member being mounted on the support member at the central region and restrained against movement away from the central region by elastic forces caused by the increasing circumference of the support member away from the central region.
- 14. The fiber optic sensor of claim 12 wherein the base portions are generally cylindrical and the central region is formed as a groove having a pair of edges defined by a pair of spaced-apart diameter steps in the support member and wherein the shear damper has a pair of end portions that abut the edges of the groove such that the shear damper is retained within the groove.
- 15. The fiber optic sensor of claim 14 wherein the damping member is formed of a viscoelastic material and wherein the damping member is axially compressed between the edges of the groove such that the damping member is expanded radially and forced against the inner edge portion of the flexural disk.
- 16. The fiber optic sensor of claim 1 wherein the housing includes:
a first housing member that includes the first end plate, a first sidewall portion extending from an outer edge of the first end plate, and a first post extending from a central region of the first end plate; a second housing member that includes the second end plate, a second sidewall portion extending from an outer edge of the second end plate and a second post extending from the second end plate, the first and second sidewall portions each having inward facing notches at end edges thereof, the first and second housing members being arranged end-to-end such that the inward facing notches define the inward-facing groove in which the outer edge of the flexural disk is mounted and such that the first and second posts are aligned end-to-end to define the support member.
- 17. A method for forming a fiber optic sensor that includes a flexural disk having a pair of fiber optic coils mounted on opposite sides thereof and optically coupled together to form an interferometer that produces an output signal in response to acceleration of the flexural disk, comprising the steps of:
forming a housing to have first and second end plates with a sidewall extending therebetween, the sidewall being formed to have an inwardly facing groove therein; mounting the flexural disk in the inwardly facing groove; mounting a compressive damper in the housing; and arranging the compressive damper to exert a compressive force on the flexural disk to control movement thereof in response to acceleration of the flexural disk along a sensing axis and thereby control the output signal amplitude.
- 18. The method of claim 17 wherein the step of mounting a compressive damper in the housing comprises the steps of:
mounting a first compressive damping member between a first side of the flexural disk and the first end plate; and mounting a second compressive damping member between a second side of the flexural disk and the second end plate.
- 19. The method of claim 18 including the steps of:
forming a support member that extends between oppositely facing portions of the first and second end plates; forming each of the first and second compressive damping members to comprise a cylinder formed of a viscoelastic material having a central passage therein; and mounting the first and second damping members in the housing such that the support member extends through the central passages in the first and second compressive damping members.
- 20. The method of claim 17 including the steps of forming each of the end plates to have ribbed inner surfaces with a plurality of ribs extending away from the end plates inward in the housing.
- 21. The method of claim 20 including the step of arranging the ribs to provide stiffening such that resonance of the housing is greater than the selected operational frequency range.
- 22. The method of claim 21 including the step of forming the ribbed inner surfaces of the end plates to provide the housing with a mass that enables the fiber optic sensor to be neutrally buoyant in water.
- 23. The fiber optic sensor of claim 20 including the step of arranging the plurality of ribs to axially compress the first and second compressive damping members.
- 24. The method of claim 23 including the step of arranging the ribs to extend radially between the support member and the sidewall of the housing.
- 25. The method of claim 24, further including the steps of:
connecting an optical coupler to the first and second fiber optic coils; and forming slots in an adjacent pair of ribs in the first end plate for mounting the optical coupler in the housing.
- 26. The method of claim 25, further comprising the step of providing a plurality of routing tabs that extend inward from the sidewall for retaining optical fibers in selected positions in the housing.
- 27. The method of claim 16, further comprising the steps of:
forming the flexural disk to include a central passage therethrough; mounting the flexural disk in the housing such that the central support extends through the central passage in the flexural disk with an inner edge of the central passage in the flexural disk being spaced apart from the support member; mounting a shear damper on the central support member; and arranging the shear damper to exert a radial force on the inner edge of the flexural disk to dampen vibrations of the flexural member and thereby further control the output signal amplitude over a selected frequency range.
- 28. The method of claim 27, including the steps of:
forming the support member to have a pair of base portions connected to the first and second end plates; and mounting the shear damping at a central region of the support member between the base portions and being restrained against lengthwise motion relative to the support member.
- 29. The method of claim 28 including the steps of:
forming the support member to have a circumference that increases lengthwise away from the central region; forming the shear damper to comprise a length of tubing formed of a viscoelastic material; mounting the shear damper on the support member at the central region; and restraining the shear damper against movement away from the central region by elastic forces caused by the increasing circumference of the support member away from the central region.
- 30. The method of claim 26 including the steps of:
forming the base portions to be generally cylindrical; forming the central region as a groove having a pair of edges defined by a pair of spaced-apart diameter steps in the support member; and arranging end portions of the shear damper to abut the end edges of the groove such that the shear damper is retained within the groove.
- 31. The method of claim 30 including the steps of:
forming the shear damper to comprise a viscoelastic material; and axially compressing the shear damper between the end edges of the groove such that the damping member is expanded radially and forced against the inner edge portion of the flexural disk.
- 32. The method of claim 17 including the steps of:
forming a first housing member that includes the first end plate, a first sidewall portion extending from an outer edge of the first end plate and a first post extending from a central region of the first end plate; forming a second housing member that includes the second end plate, a second sidewall portion extending from an outer edge of the second end plate and a second post extending from the second end plate; forming the first and second sidewall portions to each have inward facing notches at end edges thereof; and arranging the first and second housing members end-to-end such that the inward facing notches define the inward-facing groove in which the outer edge of the flexural disk is mounted and such that the first and second posts are aligned end-to-end to define the support member.
Government Interests
[0001] Statement of Government Rights: The United States government has rights in this invention under contract N00024-99-C-6332.