FAULT-TOLERANT DISTRIBUTED FIBER OPTIC INTRUSION DETECTION

• US 20100117830A1
• Filed: 12/06/2007
• Published: 05/13/2010
• Est. Priority Date: 12/29/2006
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Hartog, Arthur H., Strong, Andrew
• Granted Patent: US 8,947,232 B2
• Time in Patent Office: Days
• US Class Current: 340/555
• 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: G08B 13/186 using light guides, e.g. optical fibres

Abstract

An intrusion detection system for monitoring a premises includes at least one optical cable that houses at least one optical fiber and extends about the premises. Optical time domain reflectometry (OTDR) means is operably coupled to opposite first and second ends of the at least one optical fiber. The OTDR means includes first signal processing circuitry that analyzes the backscatter signal received via the first end of the at least one optical fiber in order to detect an intrusion of the premises, and second signal processing circuitry that analyzes the backscatter signal received via the second end of the at least one optical fiber in order to detect an intrusion of the premises. The redundancy of intrusions decisions made by the first and second signal processing circuitry can be verified. The system preferably further includes means for detecting a break in the at least one fiber, for identifying location of the break, for outputting to a user the location of the break, and for raising an alarm indicating the break.

Claims

1. An intrusion detection system for monitoring a premises comprising:

at least one optical cable that extends about the premises, the at least one optical cable comprising at least one optical fiber having a first end opposite a second end; and

optical time domain reflectometry means, operably coupled to the first and second ends of the at least one optical fiber, comprising first signal processing circuitry that analyzes the backscatter signal received via the first end of the at least one optical fiber in order to detect an intrusion of the premises, and second signal processing circuitry that analyzes the backscatter signal received via the second end of the at least one optical fiber in order to detect an intrusion of the premises.

2. An intrusion detection system according to claim 1, further comprising:

control means, operably coupled to the first signal processing circuitry and the second signal processing circuitry, for verifying redundancy of intrusions decisions made by the first and second signal processing circuitry.

3. An intrusion detection system according to claim 2, wherein:

said control means comprises a first part operably coupled to said first signal processing means, a second part operably coupled to said second signal processing means and remotely located therefrom, and communication means for communicating data between the first and second parts.

4. An intrusion detection system according to claim 1, further comprising:

means for detecting a break in the at least one fiber.

5. An intrusion detection system according to claim 4, further comprising:

means for identifying location of the break in the at least one optical fiber.

6. An intrusion detection system according to claim 5, further comprising:

means for outputting the location of the break in the at least one optical fiber to a user.

7. An intrusion detection system according to claim 4, further comprising:

means, operating in response to detection of the break, for raising an alarm indicating the break in the at least one optical fiber.

8. An intrusion detection system according to claim 1, wherein:

said first signal processing circuitry stores backscatter signal data in a first set of time bins corresponding to different lengths of the at least one optical fiber and analyzes interference patterns represented by the backscatter signal data stored in the respective time bins of the first set over time in order to make a first intrusion decision; and

said second signal processing circuitry stores backscatter signal data in a second set of time bins corresponding to different lengths of the at least one optical fiber and analyzes interference patterns represented by the backscatter signal data stored in the respective time bins of the second set over time in order to make a second intrusion decision.

9. An intrusion detection system according to claim 1, comprising:

a optical cable housing a pair of optical fibers each having a first end opposite a second end, wherein the first end of one optical fiber of the optical fiber pair is operably coupled to the optical time domain reflectometry means, and the second end of the other optical fiber of the optical fiber pair is operably coupled to the optical time domain reflectometry means.

10. An intrusion detection system according to claim 9, wherein:

the optical time domain reflectometry means includes

a laser source for generating optical pulses,

an optical detector,

a directional coupler and an optical switch, operably coupled between said laser source and said optical fiber pair, that directs said optical pulses over said optical fiber pair in a time-division-multiplexed manner and that directs scatter that propagates back along said optical fiber pair to said optical detector in a time-division-multiplexed manner,

wherein the first signal processing circuitry analyzes the backscatter signal received via the first end of the one optical fiber in order to detect an intrusion of the premises, and

wherein the second signal processing circuitry analyzes the backscatter signal received via the second end of the other optical fiber in order to detect an intrusion of the premises.

11. An intrusion detection system according to claim 9, wherein:

the optical time domain reflectometry means includes

a first laser source for generating optical pulses,

a first optical detector,

a first directional coupler operably coupled between said first laser source and the first end of the one optical fiber of said optical fiber pair, that directs said optical pulses generated by the first laser source over the one optical fiber and that directs scatter that propagates back along the one optical fiber to said first optical detector, wherein the first signal processing circuitry analyzes the backscatter signal received via the one optical fiber in order to detect an intrusion of the premises,

a second laser source for generating optical pulses,

a second optical detector, and

a second directional coupler operably coupled between said second laser source and the other optical fiber of said optical fiber pair, that directs said optical pulses generated by the second laser source over the other optical fiber and that directs scatter that propagates back along the other optical fiber to said second optical detector, wherein the second signal processing circuitry analyzes the backscatter signal received via the other optical fiber in order to detect an intrusion of the premises.

12. An intrusion detection system according to claim 1, comprising:

an optical cable housing an optical fiber having a first end opposite a second end.

13. An intrusion detection system according to claim 12, wherein:

the optical time domain reflectometry means includes

a first laser source for generating optical pulses at a first wavelength,

a first optical detector,

a first directional coupler operably coupled between said first laser source and the first end of said optical fiber, that directs said optical pulses generated by the first laser source over the optical fiber and that directs scatter that propagates back along said optical fiber to said first optical detector, wherein said first signal processing circuitry analyzes the backscatter signal at the first wavelength received via the first end of the optical fiber in order to detect an intrusion of the premises,

a second laser source for generating optical pulses at a second wavelength different than the first wavelength,

a second optical detector, and

a second directional coupler operably coupled between said second laser source and the second end of the optical fiber, that directs said optical pulses generated by the second laser source over the optical fiber and that directs scatter that propagates back along said optical fiber to said second optical detector, wherein said second signal processing circuitry analyzes the backscatter signal at the second wavelength received via the second end of the optical fiber in order to detect an intrusion of the premises.

14. A method of detecting intrusion of a premises comprising:

providing at least one optical cable that extends about the premises, the at least one optical cable comprising at least one optical fiber having a first end opposite a second end; and

coupling optical time domain reflectometry means to the first and second ends of the at least one optical fiber; and

using the optical time domain reflectometry means to analyze the backscatter signal received via the first end of the at least one optical fiber and to analyze the backscatter signal received via the second end of the at least one optical fiber in order to detect an intrusion of the premises.

15. A method according to claim 14, further comprising:

verifying redundancy of intrusions decisions based upon the analysis of the separate backscatter signals received via the first and second ends of the at least one optical fiber.

16. A method according to claim 14, further comprising:

detecting a break in the at least one fiber based upon the analysis of the separate backscatter signals received via the first and second ends of the at least one optical fiber.

17. A method according to claim 16, further comprising:

identifying location of the break in the at least one optical fiber.

18. A method according to claim 17, further comprising:

outputting to a user the location of the break in the at least one optical fiber.

19. A method according to claim 16, further comprising:

in response to detection of the break, raising an alarm indicating the break in the at least one optical fiber.

20. A method according to claim 14, wherein:

the optical time domain reflectometry means stores backscatter signal data in a set of time bins corresponding to different lengths of the at least one optical fiber and analyzes interference patterns represented by the backscatter signal data stored in the respective time bins of the set over time in order to make intrusion decisions.

21. A method according to claim 14, wherein:

the at least one optical cable comprises an optical cable housing a pair of optical fibers each having a first end opposite a second end, wherein the first end of one of the optical fiber pair is operably coupled to the optical time domain reflectometry means, and the second end of the other one of the optical fiber pair is operably coupled to the optical time domain reflectometry means.

22. A method according to claim 21, wherein:

the optical time domain reflectometry means includes

a laser source for generating optical pulses,

an optical detector, and

a directional coupler and an optical switch, operably coupled between said laser source and said optical fiber pair, that directs said optical pulses over said optical fiber pair in a time-division-multiplexed manner and that directs scatter that propagates back along said optical fiber pair to said optical detector in a time-division-multiplexed manner,

wherein the first signal processing circuitry analyzes the backscatter signal received via the first end of the one optical fiber in order to detect an intrusion of the premises, and

wherein the second signal processing circuitry analyzes the backscatter signal received via the second end of the other optical fiber in order to detect an intrusion of the premises.

23. A method according to claim 21, wherein:

the optical time domain reflectometry means includes

a first laser source for generating optical pulses,

a first optical detector,

a first directional coupler operably coupled between said first laser source and the first end of the one optical fiber of said optical fiber pair, that directs said optical pulses generated by the first laser source over the one optical fiber and that directs scatter that propagates back along the one optical fiber to said first optical detector, wherein the first signal processing circuitry analyzes the backscatter signal received via the one optical fiber in order to detect an intrusion of the premises,

a second laser source for generating optical pulses,

a second optical detector, and

a second directional coupler operably coupled between said second laser source and the other optical fiber of said optical fiber pair, that directs said optical pulses generated by the second laser source over the other optical fiber and that directs scatter that propagates back along the other optical fiber to said second optical detector, wherein the second signal processing circuitry analyzes the backscatter signal received via the other optical fiber in order to detect an intrusion of the premises.

24. A method according to claim 14, wherein:

the at least one optical cable comprises an optical cable housing an optical fiber having a first end opposite a second end.

25. A method according to claim 24, wherein:

the optical time domain reflectometry means includes

a first laser source for generating optical pulses at a first wavelength,

a first optical detector,

a first directional coupler operably coupled between said first laser source and the first end of said optical fiber, that directs said optical pulses generated by the first laser source over the optical fiber and that directs scatter that propagates back along said optical fiber to said first optical detector, wherein said first signal processing circuitry analyzes the backscatter signal at the first wavelength received via the first end of the optical fiber in order to detect an intrusion of the premises,

a second laser source for generating optical pulses at a second wavelength different than the first wavelength,

a second optical detector, and

a second directional coupler operably coupled between said second laser source and the second end of the optical fiber, that directs said optical pulses generated by the second laser source over the optical fiber and that directs scatter that propagates back along said optical fiber to said second optical detector, wherein said second signal processing circuitry analyzes the backscatter signal at the second wavelength received via the second end of the optical fiber in order to detect an intrusion of the premises.