Fiber optic self-multiplexing amplified ring transducer and force transfer sensor with pressure compensation

• US 5,589,937 A
• Filed: 05/02/1995
• Issued: 12/31/1996
• Est. Priority Date: 10/31/1994
• Status: Expired due to Fees

• Current Assignee: Navy Department of United States As Represented By The Scretary of Navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Brininstool, Michael R.
• Primary Examiner(s): Turner, Samuel A.
• Assistant Examiner(s): MERLINO, AMANDA H
• Application Number:
  US08/434,366
• Time in Patent Office: 609 Days
• Field of Search: 356/345, 356/380, 356/352, 250/227.14, 250/227.18, 250/227.19, 250/227.27
• US Class Current: 356/480
• CPC Class Codes: G01D 5/35335 Aspects of emitters or receivers used by an interferometer in an optical fibre sensor arrangement using multiple sensor devices using multiplexing techniques G01D5/35383
• CPC Class Codes: G01D 5/35348 using stimulated emission to detect the measured quantity
• CPC Class Codes: G01L 1/243 using means for applying force perpendicular to the fibre axis
• CPC Class Codes: G01L 1/247 using distributed sensing elements, e.g. microcapsules along a single optical fibre G01L1/242

Abstract

A fiber optic sensor system includes a first optical power source which icts a light pulse into an optical fiber loop system. The light pulse circulates in the optical fiber loop system at a circulation frequency. The optical fiber loop system includes a transducer which modulates the circulation frequency in response to detecting a changing physical condition, a filter, polarization controller, an isolator, and an optical fiber gain medium for amplifying the light pulse. A second optical power source provides optical energy to the optical fiber gain medium. A detector system transforms a portion of the light pulse received from the optical fiber loop system into an output signal representing the circulation frequency.

Claims

1. A fiber optic sensor system, comprising:

a first optical power source for generating a light pulse;

an optical fiber loop system coupled to receive said light pulse, wherein said light pulse circulates in said optical fiber loop system at a circulation frequency, and which includes;

a transducer which modulates said circulation frequency in response to detecting a changing physical condition;

an optical fiber gain medium for amplifying said light pulse;

a second optical power source for providing optical energy to said optical fiber gain medium; and

a detector system for receiving a portion of said light pulse received from said optical fiber loop system and generating an output signal representing said circulation frequency.

2. The system of claim 1 wherein said first optical power source includes a laser diode.

3. The system of claim 1 wherein said first optical power source includes a light emitting diode.

4. The system of claim 1 wherein said transducer includes a coil of optical fiber.

5. The system of claim 1 wherein said optical fiber gain medium includes an erbium doped fiber amplifier.

6. The system of claim 1 wherein said detector system includes a photodiode.

7. The system of claim 1 wherein said detector system includes a phototransistor.

8. The system of claim 1 wherein said detector system includes a avalanche photodiode.

9. The system of claim 1 wherein said optical fiber loop system includes an optical isolator.

10. The system of claim 1 wherein said optical fiber loop system includes a polarization controller.

11. The system of claim 1 wherein said detector system includes a Fourier analyzer.

12. The system of claim 1 wherein said detector system includes an FM receiver.

13. The system of claim 1 further including a first optical coupler optically coupled between said first optical power source and said optical fiber loop system.

14. The system of claim 1 further including a second optical coupler optically coupled between said optical fiber loop system and said second optical power source.

15. A fiber optic sensor system, comprising:

a first optical power source for generating a light pulse;

an optical fiber loop system coupled to receive said light pulse, wherein said light pulse circulates in said optical fiber loop system at a circulation frequency, and which includes;

a transducer which responds to a changing physical condition by modulating said circulation frequency;

an optical fiber gain medium for amplifying said light pulse; and

a detector system for transforming a portion of said light pulse received from said optical fiber loop system into an output signal representing said circulation frequency.

16. A multiplexed fiber optic sensor system, comprising:

a first optical power source for generating a light pulse;

multiple optical fiber loop systems coupled to receive a portion of said light pulse, wherein said portion of said light pulse circulates in each said optical fiber loop system at a unique circulation frequency, where each said optical fiber loop system includes;

a transducer which modulates said circulation frequency in response to detecting a changing physical condition;

an optical fiber gain medium for amplifying said portion of said light pulse circulating in said optical fiber loop system;

a second optical power source for providing optical energy to said optical fiber gain medium in each of said fiber optic loop systems; and

a detector system optically coupled to receive a portion of said light pulse from said optical fiber loop systems for generating output signals representing said circulation frequencies of said light pulses circulating said optical fiber loop systems.

17. The system of claim 16 wherein said first optical power source includes a laser diode.

18. The system of claim 16 wherein said first optical power source includes a light emitting diode.

19. The system of claim 16 wherein said transducer of each said optical fiber loop system includes a coil of optical fiber.

20. The system of claim 16 wherein said optical fiber gain medium of each said optical fiber loop system includes an erbium doped fiber amplifier.

21. The system of claim 16 wherein said detector system includes a photodiode.

22. The system of claim 16 wherein said detector system includes a phototransistor.

23. The system of claim 16 wherein said detector system includes an avalanche photodiode.

24. The system of claim 16 wherein each said optical fiber loop system includes an optical isolator.

25. The system of claim 16 wherein each said optical fiber loop system includes a polarization controller.

26. The system of claim 16 wherein said detector system includes a Fourier analyzer.

27. The system of claim 16 wherein said detector system includes an FM receiver.

28. The system of claim 16 further includes a first optical coupler optically coupled between said first optical power source and said optical fiber loop systems.

29. The system of claim 16 further includes a second optical coupler optically coupled between said optical fiber loop systems and said second optical power source.