FIBER OPTIC INTERFEROMETER AND METHOD FOR DETERMINING PHYSICAL STATE PARAMETERS IN THE INTERIOR OF A FIBER COIL OF A FIBER OPTIC INTERFEROMETER

• US 20110149293A1
• Filed: 07/17/2009
• Published: 06/23/2011
• Est. Priority Date: 08/28/2008
• Status: Active Grant

• Current Assignee: Northrop Grumman Litef Gmbh (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Litef Gmbh (Northrop Grumman Corporation)
• Inventors: Dorner, Georg
• Granted Patent: US 8,982,356 B2
• Time in Patent Office: Days
• US Class Current: 356/460
• CPC Class Codes: G01C 19/721 Details

Abstract

A fiber-optic interferometer comprising an optical fiber wound to form a fiber coil into which two partial light beams of a first light source can be coupled. The Bragg structure is integrated into the fiber coil. Said Bragg structure comprises an optical fiber having a periodically varying refractive index. In a method for determining physical state parameters in the interior of a fiber coil of a fiber optic interferometer information about physical state parameters in the interior of the fiber coil is obtained on the basis of the reflection wavelength of a Bragg structure comprising an optical fiber having a periodically varying refractive index is integrated into the fiber coil.

Claims

1. A rate of rotation sensor comprising a fiber optic interferometer comprising an optical fiber comprising a core material, which is wound to form a fiber coil and into which two partial light beams of a first light source can be coupled, wherein a part of the core material of the optical fiber is embodied as a Bragg structure having a periodically varying refractive index, wherein the fiber optic interferometer is suitable for outputting signals from which physical state parameters in the interior of the fiber coil can be determined.

2. The rate of rotation sensor as claimed in claim 1, characterized in that the interferometer has a second light source which is arranged in such a way that a light beam emitted by it can be coupled into the optical fiber of the Bragg structure having a periodically varying refractive index.

3. The rate of rotation sensor as claimed in either of claims 1 and 2, characterized in that the interferometer has a beam splitter, by means of which a light beam coupled into the beam splitter can be split into two partial light beams and which is arranged in such a way that the two partial light beams can respectively be coupled into an end of the optical fiber.

4. The rate of rotation sensor as claimed in any of the preceding claims, characterized in that the interferometer has a coupler, by means of which the two partial light beams emerging from the optical fiber can be superimposed to form a light beam.

5. The rate of rotation sensor as claimed in any of the preceding claims, characterized in that the optical fiber having a periodically varying refractive index forms a section of a further optical fiber, which is wound in parallel fashion with respect to the optical fiber into which the two partial light beams of the first light source can be coupled, to form the fiber coil.

6. The rate of rotation sensor as claimed in any of claims 1 to 4, characterized in that the optical fiber having a periodically varying refractive index forms a section of the optical fiber into which the two partial light beams of the first light source can be coupled.

7. The rate of rotation sensor as claimed in claim 2, characterized in that the wavelength range of the light emitted by the second light source does not overlap the wavelength range of the light emitted by the first light source.

8. The rate of rotation sensor as claimed in claim 6 or 7, characterized in that a wavelength-selective device is provided, which is coupled to the optical fiber in such a way that the light emerging from the optical fiber can be decomposed into individual wavelength ranges.

9. The rate of rotation sensor as claimed in any of the preceding claims, characterized in that the interferometer comprises a photodetector (34, 134), which is arranged in such a way that a light beam that has passed through the optical fiber having a periodically varying refractive index is detected by it.

10. The rate of rotation sensor as claimed in claim 9, characterized in that the photodetector is coupled to an evaluation unit, by means of which physical state parameters in the interior of the fiber coil can be determined on the basis of the reflection wavelength of the Bragg structure.

17. The rate of rotation sensor as claimed in claim 1, characterized in that the interferometer furthermore comprises a coupler, in which the two partial light beams are superimposed, and additionally an element for compensation of a propagation time change brought about by a change in the physical state parameter.

11. A method for determining the rate of rotation, in which two partial light beams are coupled into an optical fiber wound to form the fiber coil of a fiber optic interferometer, characterized in that information about physical state parameters in the interior of the fiber coil is additionally obtained on the basis of the reflection and/or transmission wavelength of a Bragg structure embodied as part of the optical fiber having a periodically varying refractive index.

12. The method as claimed in claim 11, characterized in that both the light emitted by a first light source and the light emitted by a second light source are coupled into an optical fiber wound to form the fiber coil, wherein at least one section of the optical fiber forms the Bragg structure having a periodically varying refractive index.

13. The method as claimed in claim 12, characterized in that the wavelength range of the light emitted by the second light source does not overlap the wavelength range of the light emitted by the first light source.

14. The method as claimed in claim 11, characterized in that the light emitted by a first light source is coupled into a first optical fiber, and in that the light emitted by a second light source is coupled into a second optical fiber, wherein the second optical fiber is wound in parallel fashion with respect to the first optical fiber to form the fiber coil, and wherein the optical fiber having a periodically varying refractive index forms a section of the second optical fiber.

15. The method as claimed in claim 11, characterized in that a phase modulator is driven depending on the information obtained about physical state parameters in the interior of the fiber coil, which phase modulator is suitable for modulating the phase of a light beam that has passed through an optical fiber wound to form the fiber coil.

16. The method as claimed in claim 11, characterized in that the information about physical state parameters in the interior of the fiber coil comprises the temperature and the stress in the region of the optical fiber having a periodically varying refractive index and the time-dependent and location-dependent changes thereof.

18. The method as claimed in claim 11, characterized in that the two partial light beams are superimposed and a propagation time change of the partial light beams that is brought about by a change in the physical state parameter is compensated for.