Fiber optic sensor using a Bragg fiber

• US 8,068,231 B2
• Filed: 05/06/2010
• Issued: 11/29/2011
• Est. Priority Date: 08/20/2002
• Status: Expired due to Term

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Digonnet, Michel J. F.
• Primary Examiner(s): Toatley; Gregory J.
• Assistant Examiner(s): Richey; Scott
• Application Number:
  US12/775,379
• Publication Number:
  US 20100220332A1
• Time in Patent Office: 572 Days
• Field of Search: 356/459, 356/460, 356/461, 356/483
• US Class Current: 356/460
• CPC Class Codes: G01C 19/722 of the mechanical construction
• CPC Class Codes: G02B 6/02328 Hollow or gas filled core
• CPC Class Codes: G02B 6/02361 Longitudinal structures forming multiple layers around the core, e.g. arranged in multiple rings with each ring having longitudinal elements at substantially the same radial distance from the core, having rotational symmetry about the fibre axis

Abstract

An optical sensor includes an optical coupler configured to receive a first optical signal and to split the first optical signal into a second optical signal and a third optical signal. The optical sensor further includes a Bragg fiber in optical communication with the optical coupler. The second optical signal and the third optical signal counterpropagate through the Bragg fiber and return to the third port and the second port, respectively.

Claims

1. An optical gyroscope comprising:

an optical coupler configured to receive a first optical signal and to split the first optical signal into a second optical signal and a third optical signal; and

a Bragg fiber in optical communication with the optical coupler such that the second optical signal and the third optical signal counterpropagate through the Bragg fiber and return to the optical coupler, wherein interference between the second optical signal and the third optical signal after the second and third optical signals have counterpropagated through the Bragg fiber is responsive to rotations of at least a portion of the Bragg fiber.

2. The optical gyroscope of claim 1, further comprising a light source having an output that emits the first optical signal and is in optical communication with the optical coupler.

3. The optical gyroscope of claim 2, wherein the light source comprises a superfluorescent light source.

4. The optical gyroscope of claim 3, wherein the superfluorescent light source comprises an erbium-doped superfluorescent fiber source.

5. The optical gyroscope of claim 2, wherein the light source has a spectral distribution with a full width at half maximum of about 1 nanometer or larger.

6. The optical gyroscope of claim 2, wherein the light source has a spectral distribution with a full width at half maximum of less than 1 nanometer.

7. The optical gyroscope of claim 1, further comprising an optical detector in optical communication with the optical coupler to receive the second optical signal and the third optical signal after the second and third optical signals have counterpropagated through the Bragg fiber.

8. The optical gyroscope of claim 1, wherein the Bragg fiber comprises a hollow core.

9. The optical gyroscope of claim 8, wherein the core contains air.

10. The optical gyroscope of claim 1, wherein the Bragg fiber is a coil.

11. The optical gyroscope of claim 10, wherein the Bragg fiber coil is wound around a spool such that differential phase shifts due to asymmetric variations of the temperature of the Bragg fiber coil with respect to a mid-point of the Bragg fiber coil are reduced.

12. A method for sensing rotation, the method comprising:

providing a light signal;

propagating a first portion of the light signal in a first direction through a Bragg fiber;

propagating a second portion of the light signal in a second direction through the Bragg fiber, the second direction opposite to the first direction;

optically interfering the first and second portions of the light signal after the first and second portions of the light signal propagate through the Bragg fiber, thereby producing an optical interference signal;

subjecting at least a portion of the Bragg fiber to a rotation; and

measuring variations in the optical interference signal caused by the rotation.

13. The method of claim 12, wherein the Bragg fiber comprises a core, the first portion of the light signal substantially confined to the core, the second portion of the light signal substantially confined to the core.

14. The method of claim 13, wherein the core is hollow.

15. The method of claim 14, wherein the core comprises air.

16. An optical gyroscopic system comprising:

an optical coupler configured to receive a first optical signal and to split the first optical signal into a second optical signal and a third optical signal; and

an optical waveguide having a hollow core generally surrounded by a cladding, the optical waveguide in optical communication with the optical coupler such that the second optical signal and the third optical signal counterpropagate through the optical waveguide and return to the optical coupler, the cladding of the optical waveguide substantially confining the counterpropagating second optical signal and third optical signal within the hollow core, wherein interference between the second optical signal and the third optical signal after the second and third optical signals have counterpropagated through the optical waveguide is responsive to rotations of at least a portion of the optical waveguide.

17. The optical gyroscopic system of claim 16, further comprising a light source in optical communication with the optical coupler, the light source configured to emit the first optical signal.

18. The optical gyroscopic system of claim 16, further comprising an optical detector in optical communication with the optical coupler, the optical detector receiving the second optical signal and the third optical signal after having counterpropagated through the optical waveguide.

19. A method for sensing rotation, the method comprising:

providing a light signal;

propagating a first portion of the light signal in a first direction through a Bragg optical waveguide having a hollow core generally surrounded by a cladding;

propagating a second portion of the light signal in a second direction through the optical waveguide, the second direction opposite to the first direction;

optically interfering the first and second portions of the light signal after the first and second portions of the light signal propagate through the Bragg optical waveguide, thereby producing an optical interference signal;

subjecting at least a portion of the optical waveguide to a rotation; and

measuring variations in the optical interference signal caused by the rotation.

20. A gyroscopic sensor comprising an optical waveguide having a hollow core generally surrounded by a cladding, wherein a first optical signal and a second optical signal counterpropagate through the optical waveguide, the cladding of the optical waveguide substantially confining the counterpropagating first optical signal and second optical signal within the hollow core, wherein interference between the first optical signal and the second optical signal is responsive to rotations of at least a portion of the optical waveguide.

21. The gyroscopic sensor of claim 20, wherein the gyroscopic sensor comprises a Sagnac interferometer.

22. A perturbation sensor comprising an optical waveguide having a hollow core generally surrounded by a cladding, wherein a first optical signal and a second optical signal counterpropagate through the optical waveguide, the cladding of the optical waveguide substantially confining the counterpropagating first optical signal and second optical signal within the hollow core, wherein interference between the first optical signal and the second optical signal is responsive to perturbations applied to at least a portion of the optical waveguide, wherein the perturbations are selected from the group consisting of:

magnetic fields, electric fields, pressure, displacements, twisting, and bending applied to at least a portion of the optical waveguide.