Perimeter detection

• US 20050077455A1
• Filed: 08/13/2004
• Published: 04/14/2005
• Est. Priority Date: 08/13/2003
• Status: Active Grant

• Current Assignee: Zygo Corporation (Ametek Incorporated)
• Original Assignee: Zygo Corporation (Ametek Incorporated)
• Inventors: Ranalli, Eliseo Romolo, Kondis, John, Hellman, Scott, Townley-Smith, Paul A.
• Granted Patent: US 7,488,929 B2
• Time in Patent Office: Days
• US Class Current: 250/227.270
• CPC Class Codes: G08B 13/124 with the breaking or disturbance being optically detected, e.g. optical fibers in the perimeter fence
• CPC Class Codes: G08B 13/186 using light guides, e.g. optical fibres

Abstract

A fiber optic perimeter detection system includes a receiver to receive output light signals from sensors positioned at different regions, each sensor including a sensing fiber. Each sensor generates an output light signal having a specified wavelength, the output light signal having a property that varies when stress is induced in the sensing fiber. The perimeter detection system includes a memory to store information related to a mapping between the wavelengths of the output light signals and the regions where the sensors are positioned.

Claims

1. An apparatus comprising:

a receiver to receive output light signals from sensors positioned at different regions, each sensor including a sensing fiber, each sensor to generate an output light signal having a specified wavelength, the output light signal having a property that varies when stress is induced in the sensing fiber; and

a memory to store information related to a mapping between the wavelengths of the output light signals and the regions where the sensors are positioned.

2. The apparatus of claim 1, further comprising a transmitter to transmit light signals having multiple wavelengths to the sensors.

3. The apparatus of claim 1, further comprising a display to indicate a particular region when there is a change in an output light signal having a wavelength that maps to the particular region.

4. The apparatus of claim 1 in which each of at least a subset of the sensors comprises a fiber optic sensor that transmits light having a specified wavelength through the sensing fiber.

5. The apparatus of claim 4 in which at least one region has sensing fibers of at least two fiber optic sensors.

6. The apparatus of claim 4 in which the fiber senses pressure applied to the fiber.

7. The apparatus of claim 4 in which each fiber optic sensor comprises a wavelength division multiplexing (WDM) filter that allows a light signal having a specific wavelength to pass.

8. The apparatus of claim 4 in which the output light signal of each of at least a subset of the fiber optic sensors comprises an interference signal based on an interference of light signals, at least one signal transmitted through the sensing fiber.

9. The apparatus of claim 8 in which the sensing fiber is coupled to a reflector.

10. The apparatus of claim 8 in which the interference signal is based on an interference of light signals entering and exiting opposing ends of the sensing fiber.

11. The apparatus of claim 1, further comprising one or more fiber cables to transmit the light signals from the transmitter to the fiber optic sensors and to transmit the output light signals from the fiber optic sensors to the receiver.

12. The apparatus of claim 1 in which the property comprises at least one of a phase and an amplitude of the output light signal.

13. An apparatus comprising:

a fiber optic sensor to generate an interference signal based on two signals, at least one signal traveling through a sensing fiber, the interference signal varying in phase and/or amplitude when stress is induced in the sensing fiber;

a detector to detect the interference signal; and

a data processor to detect changes in the interference signal.

14. The apparatus of claim 13 in which the sensor comprises a reference fiber and the sensing fiber, the interference signal being generated by superimposing a reference signal that traverses the reference fiber and a sensor signal that traverses the sensing fiber.

15. The apparatus of claim 13 in which the interference signal is generated based on an interference of two signals traveling the sensing fiber in opposite directions.

16. A perimeter sensing system comprising:

fiber optic sensors positioned at different regions, each fiber optic sensor including a sensing fiber, each fiber optic sensor to generate an output light signal having a specified wavelength, the output light signal having a property that varies when stress is induced in the sensing fiber;

a transmitter to transmit light signals having multiple wavelengths to the fiber optic sensors;

a receiver to receive the output light signals from the sensors;

a memory to store information related to a mapping between the wavelengths of the output light signals and the regions where the fiber optic sensors are positioned; and

a display to indicate a change in the one or more conditions in a particular region when there is a change in an output light signal having a wavelength that maps to the particular region.

17. The system of claim 16 in which each fiber optic sensor transmits light having a specified wavelength through the sensing fiber.

18. The system of claim 17 in which each fiber optic sensor comprises a wavelength division multiplexing filter that allows a light signal having a specific wavelength to pass to the sensing fiber.

19. The system of claim 16 in which the output light signal of each of at least a subset of the fiber optic sensors comprises an interference signal based on an interference of light signals, at least one signal transmitted through the sensing fiber.

20. The system of claim 16, further comprising fiber cables to transmit light signals from the transmitter to one of the fiber optic sensors, from the fiber optic sensors to the receiver, and from one fiber optic sensor to anther fiber optic sensor.

21. The system of claim 16 in which the property comprises at least one of a phase and an amplitude of the output light signal.

22. A storage medium comprising:

a database that stores information about a mapping between locations of fiber optic sensors and wavelengths associated with the fiber optic sensors, each fiber optic sensor having a sensing fiber and is associated with a particular wavelength, each fiber optic sensor generating an output that is sensitive to stress induced in the sensing fiber.

23. The storage medium of claim 22 in which the database stores information about the outputs of the fiber optic sensors under various environment conditions.

24. The storage medium of claim 23 in which the environment conditions include at least one of temperature, type of soil in the vicinity of the sensing fiber, bury depth of the sensing fiber, and pressure applied to the sensing fiber.

25. A method comprising:

sensing physical pressure applied to different regions based on light signals having different wavelengths and on information about a mapping between the wavelengths and the regions.

26. The method of claim 25, further comprising sensing the one or more conditions at a region using at least one sensor that is positioned at the region, each sensor generating an output light signal having a specified wavelength, the output light signal having a property that changes when the pressure applied to the region changes.

27. The method of claim 26, in which each of at least a subset of the sensors comprises a fiber optic sensor that transmits light having a specified wavelength through a sensing fiber.

28. The method of claim 27, further comprising, using each fiber optic sensor to generate an interference signal based on an interference of light signals, at least one of the light signals being transmitted through the sensing fiber.

29. The method of claim 28 in which generating the interference signal comprises overlapping a reference light signal and the light signal transmitted through the sensing fiber with.

30. The method of claim 28 in which generating the interference signal comprises sending light signals into the sensing fiber through opposing ends of the fiber.

31. The method of claim 26, further comprising transmitting light signals having multiple wavelengths to the sensors.

32. The method of claim 31, further comprising, at each fiber optic sensor, filtering the light signals to allow a light signal having a specified wavelength to pass and to reflect the other light signals.

33. A method comprising:

generating an interference signal based on two signals, at least one signal traveling through a sensing fiber, the interference signal varying in phase and/or amplitude when stress is induced in the sensing fiber;

detecting the interference signal; and

detecting changes in the interference signal.

34. The method of claim 33 in which the two signals comprises a reference signal and a sensor signal, the reference signal traveling a reference fiber that is insensitive to changes in an environment, the sensor signal traveling a sensing fiber that is sensitive to changes in the environment.

35. The method of claim 33 in which the two signals travel along a common sensing fiber in opposite directions.

36. A perimeter monitoring method comprising:

sensing one or more conditions using fiber optic sensors that are positioned at different regions, each fiber optic sensor including a sensing fiber and generating an output light signal having a specified wavelength, the output light signal varying when stress is induced in the sensing fiber, at least a subset of the sensors each having an output light signal with a wavelength that is different from those of the other sensors in the subset;

receiving the output light signals from the fiber optic sensors; and

monitoring the one or more conditions at the different regions based on the output signals from the sensors and on information related to a mapping between the wavelengths of the output light signals and the regions where the sensors are positioned.

37. The method of claim 36 in which each fiber optic sensor transmits light having a specified wavelength through the sensing fiber.

38. The method of claim 37 in which sensing one or more conditions comprises sensing pressure applied to the sensing fiber.

39. The method of claim 36, further comprising transmitting light signals having multiple wavelengths to the sensors.

40. The method of claim 39, further comprising, at each fiber optic sensor, filtering the light signals to allow a light signal having a specified wavelength to pass to the sensing fiber and to reflect the other light signals.

41. A method comprising:

detecting a presence of an object in a protected area by using fiber optic sensors that are positioned at different regions in the protected area, each fiber optic sensor including a sensing fiber and generating an output light signal having a specified wavelength, the output light signal having a property that changes when stress is induced in the sensing fiber, at least a subset of the sensors each having an output light signal with a wavelength that is different from those of the other sensors in the subset.

42. The method of claim 41, further comprising receiving the output light signals from the fiber optic sensors, and monitoring the different regions based on the output signals from the sensors and on information related to a mapping between the wavelengths of the output light signals and the regions where the sensors are positioned.

43. The method of claim 41 in which the property comprises at least one of a phase and an amplitude of the output light signal.

44. A method comprising:

deploying a fiber optic sensor in an area, the fiber optic sensor including an interferometer that includes a sensing fiber, the interferometer to generate an interference signal having a property that varies when stress is induced in the sensing fiber.

45. The method of claim 44 in which the interferometer generates the interference signal based on an interference between a first signal propagating a reference path and a second signal propagating a sensor path, the sensor path including the sensing fiber.

46. The method of claim 44 in which the interferometer generates the interference signal based on an interference between two signals propagating in opposite directions through the sensing fiber.

47. A method comprising:

deploying multiple fiber optic sensors in an area, each the fiber optic sensor including a filter and a sensing fiber that is sensitive to stress, the filter allowing only light signals having a particular wavelength to be coupled to the sensing fiber to allow that sensor to generate an output signal having the particular wavelength, the output signal having a property that changes in response to stress induced in the sensing fiber, the filters in different sensors allowing light signals having different wavelengths to pass to corresponding sensing fibers.

48. The method of claim 47, further comprising linking the fiber optic sensors using transmit interconnect fibers and receive interconnect fibers, the transmit interconnect fibers to send wavelength division multiplexed signals to each of at least a subset of the sensors, the receive interconnect fibers to receive wavelength division multiplexed signals from each of at least a subset of the sensors.