Long Distance Optical Fiber Sensing System and Method

• US 20110075152A1
• Filed: 09/28/2009
• Published: 03/31/2011
• Est. Priority Date: 09/28/2009
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Inventors: Huffman, John Sinclair
• Granted Patent: US 8,345,229 B2
• Time in Patent Office: Days
• US Class Current: 356/482
• CPC Class Codes: G01D 5/35358 using backscattering to detect the measured quantity
• CPC Class Codes: G01D 5/35374 Particular layout of the fiber
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125
• CPC Class Codes: G01M 11/3109 Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR
• CPC Class Codes: G01M 11/3136 for testing of multiple fibers
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target
• CPC Class Codes: G01S 17/26 wherein the transmitted pulses use a frequency-modulated or phase-modulated carrier wave, e.g. for pulse compression of received signals
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01V 1/001 Acoustic presence detection
• CPC Class Codes: G08B 13/124 with the breaking or disturbance being optically detected, e.g. optical fibers in the perimeter fence

Abstract

A long-distance fiber optic monitoring system having a sensing unit and an analyzer that is remotely located from the sensing unit is provided. The sensing unit comprises a source of optical energy for injecting optical energy into the fiber optical cable and an optical detector configured to detect an optical return signal from the optical fiber. The detected optical return signal is associated with an acoustic signal impinging on the optical fiber. The analyzer receives a signal from the remote sensing unit via the optical fiber that is representative of the optical return signal, and determines a location of a disturbance based at least on the received signal. The representative signal can be transmitted from the remote sensing unit to the analyzer as an optical signal or via a metallic wired included with the optical fiber.

Claims

1. A long-distance monitoring system comprising:

a first optical fiber;

a sensing unit comprising;

a first source of optical energy configured to inject optical energy into the first optical fiber; and

a first optical detector configured to detect a first optical return signal from the first optical fiber, the first optical return signal associated with an acoustic signal impinging on the first optical fiber; and

an analyzer remote from the sensing unit and configured to receive a first signal via the first optical fiber representative of the first optical return signal from the remote sensing unit and determine a location of a disturbance based at least on the first received signal.

2. The system of claim 1, wherein the remote sensing unit further comprises a communication unit configured to transmit the first signal representative of the first optical return signal over the first optical fiber to the analyzer.

3. The system of claim 2, wherein the optical energy injected into the first optical fiber has a wavelength that is different from a wavelength of the transmitted first signal representative of the first optical return signal.

4. The system of claim 1, wherein the first optical fiber includes a metallic wire and the remote sensing unit further comprises a communication unit configured to transmit the signals representative of the first optical return signal over the metallic wire.

5. The system of claim 1, further comprising at least one regenerator connected to the first optical fiber.

6. The system of claim 1, wherein the first optical fiber includes a metallic wire, the system further comprising a power source configured to provide power over the metallic wire and the remote sensing unit further comprises a power subsystem configured to receive power via the metallic wire.

7. The system of claim 1, wherein the remote sensing unit is configured to be submersible.

8. The system of claim 7, wherein the remote sensing unit further comprises a cooling subsystem for water-cooling the remote sensing unit.

9. The system of claim 1, further comprising:

a second optical fiber,

wherein the remote sensing unit further comprises;

a second source of optical energy configured to inject optical energy into the second optical fiber, and

a second optical detector configured to detect a second optical return signal from the second optical fiber, the second optical return signal associated with the acoustic signal impinging on the second optical fiber, and

the analyzer is further configured to receive signals representative of the second optical return signal from the remote sensing unit and determine the location of the disturbance based at least on the first and second received signals.

10. The system of claim 1, wherein the first optical fiber is longer than 25 miles.

11. A method for determining the location of a source of acoustic energy over long-distances comprising:

injecting optical energy into a first optical fiber at a remote sensing unit;

receiving at the remote sensing unit from the first optical fiber a first optical return signal, the first optical return signal associated with an acoustic signal impinging on the first optical fiber;

transmitting from the remote sensing unit a first signal representative of the first optical return signal from the remote sensing unit to an analyzer for determination of the location of the disturbance based at least on the first transmitted signal.

12. The method of claim 11, wherein the first signal representative of the first optical return signal is transmitted over the first optical fiber.

13. The method of claim 12, wherein the optical energy injected into the first optical fiber has a wavelength that is different from a wavelength of the transmitted first signal representative of the first optical return signal.

14. The method of claim 11, wherein the first signal representative of the first optical return signal is transmitted over a metallic wire of the first optical fiber.

15. The method of claim 11, further comprising regenerating an optical signal transmitted via the first optical fiber at a regenerator.

16. The method of claim 11, further comprising receiving power via a metallic wire included in the first optical fiber.

17. The method of claim 11, wherein the remote sensing unit is configured to be submersible.

18. The method of claim 17, further comprising water-cooling the remote sensing unit.

19. The method of claim 11, further comprising:

injecting at the remote sensing unit optical energy into a second optical fiber

receiving at the remote sensing unit from the second optical fiber a second optical return signal associated with the acoustic signal impinging on the second optical fiber;

transmitting from the remote sensing unit a second signal representative of the second optical return signal from the remote sensing unit to the analyzer for determination of the location of the disturbance based at least on the first and second transmitted signal.

20. The method of claim 11, wherein the first optical fiber is longer than 25 miles.