Perimeter detection using fiber optic sensors
First Claim
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1. An apparatus comprising:
- fiber optic sensors positioned at different regions, each fiber optic sensor comprising;
a sensing fiber, anda wavelength division multiplexing filter to receive wavelength division multiplexed signals intended for multiple fiber optic sensors, allow one of the light signals having a specific wavelength to pass to the sensing fiber and prevent light signals intended for other fiber optic sensors from passing to the sensing fiber,each fiber optic sensor generating an output light signal having the specific wavelength, the output light signal having a property that varies when stress is induced in the sensing fiber, wherein the wavelength division multiplexing filter multiplexes the output light signal from the fiber optic sensor with output light signals from other fiber optic sensors to generate wavelength division multiplexed output light signals;
a receiver to receive the wavelength division multiplexed output light signals; and
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.
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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.
77 Citations
43 Claims
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1. An apparatus comprising:
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fiber optic sensors positioned at different regions, each fiber optic sensor comprising; a sensing fiber, and a wavelength division multiplexing filter to receive wavelength division multiplexed signals intended for multiple fiber optic sensors, allow one of the light signals having a specific wavelength to pass to the sensing fiber and prevent light signals intended for other fiber optic sensors from passing to the sensing fiber, each fiber optic sensor generating an output light signal having the specific wavelength, the output light signal having a property that varies when stress is induced in the sensing fiber, wherein the wavelength division multiplexing filter multiplexes the output light signal from the fiber optic sensor with output light signals from other fiber optic sensors to generate wavelength division multiplexed output light signals; a receiver to receive the wavelength division multiplexed output light signals; and 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A perimeter sensing apparatus comprising:
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a fiber optic sensor for coupling to a fiber interconnect cable, the fiber optic sensor comprising a reference fiber, a sensing fiber, and a filter, the fiber optic sensor generating an interference signal based on a reference signal and a sensing signal, the reference signal traversing the reference fiber and does not traverse the sensing fiber, the sensing signal traversing the sensing fiber and does not traverse the reference fiber, the interference signal varying in phase and/or amplitude when stress is induced in the sensing fiber, wherein the filter receives light signals intended for multiple fiber optic sensors from an upstream segment of the fiber interconnect cable, allows one of the light signals having a specific wavelength to pass to the reference fiber and the sensing fiber, and reflects the light signals intended for other fiber optic sensors to a downstream segment of the fiber interconnected cable; a detector to detect the interference signal; and a data processor to detect changes in the interference signal.
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12. A perimeter sensing apparatus comprising:
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fiber optic sensors each comprising; a sensing fiber loop, and a filter to allow an input light signal having a specific wavelength to pass to the sensing fiber loop and prevent light signals intended for other fiber optic sensors from passing to the sensing fiber loop, the fiber optic sensor generating an interference signal based on an interference of two signals split from the input light signal, the two signals traveling the sensing fiber loop in opposite directions, the interference signal varying in phase and/or amplitude when stress is induced in the sensing fiber loop; a detector to detect the interference signal; and a data processor to detect changes in the interference signal. - View Dependent Claims (13)
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14. A perimeter sensing system comprising:
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a fiber interconnect cable; and fiber optic sensors positioned at different regions and connected by the fiber interconnect cable, each fiber optic sensor comprising; a sensing fiber that branches off the fiber interconnect cable, and a filter to receive light signals intended for multiple fiber optic sensors from an upstream segment of the fiber interconnect cable, allow a light signal having a specific wavelength to pass to the sensing fiber, prevent light signals intended for other fiber optic sensors from passing to the sensing fiber, and reflect the light signals intended for other fiber optic sensors to a downstream segment of the fiber interconnected cable, each fiber optic sensor generating an output light signal having the specific wavelength, the output light signal having a property that varies when stress is induced in the sensing fiber. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A method comprising:
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at a filter of a fiber optic sensor coupled to a fiber interconnect cable, receiving light signals intended for multiple fiber optic sensors from an upstream segment of the fiber interconnect cable, passing one of the light signals having a specific wavelength, and reflecting the light signals intended for other fiber optic sensors to a downstream segment of the fiber interconnected cable; generating an interference signal based on a reference signal and a sensor signal that are derived from the light signal that passed the filter, 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 region, in which the reference signal does not travel through the sensing fiber and the sensor signal does not travel through the reference fiber; detecting the interference signal; and detecting changes in the interference signal. - View Dependent Claims (27, 28, 29)
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30. A method of monitoring a region using a plurality of sensing fiber loops, comprising:
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for each sensing fiber loop, filtering light signals having multiple wavelengths to allow an input signal having a specific wavelength to pass to the sensing fiber loop and prevent light signals intended for other sensing fiber loops from passing to the sensing fiber loop; generating an interference signal based on an interference between two signals split from the input signal, the two signals traveling along the sensing fiber loop in opposite directions, the sensing fiber loop being positioned at the region, the interference signal varying in phase and/or amplitude when stress is induced in the sensing fiber loop; detecting the interference signals from the sensing fiber loops; and detecting changes in the interference signals. - View Dependent Claims (31)
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32. A perimeter monitoring method comprising:
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sensing one or more conditions using fiber optic sensors that are positioned at different regions, each fiber optic sensor including a sensing fiber and a filter, the filter allowing a light signal having a specific wavelength to pass to the sensing fiber, the fiber optic sensor generating an output light signal having the specified wavelength, the output light signal varying when stress is induced in the sensing fiber, the filter passing corresponding light signals having a corresponding wavelength such that each sensing fiber receives light signals having the corresponding wavelength and not receive light signals intended for other sensing fibers, wherein the output light signal comprises an interference signal generated based on an interference of light signals, at least one of the light signals being transmitted through the sensing fiber; 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 fiber optic sensors and on information related to a mapping between the wavelengths of the output light signals and the regions where the fiber optic sensors are positioned. - View Dependent Claims (33, 34, 35, 36, 37, 38)
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39. A method comprising:
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deploying multiple fiber optic sensors in an area, each of the fiber optic sensors including a filter and a sensing fiber that is sensitive to stress applied to a region within the area, 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; wherein for each of at least some of the fiber optic sensors, the sensing fiber forms a loop and the fiber optic sensor generates an interference signal based on an interference between two signals propagating in opposite directions through the sensing fiber. - View Dependent Claims (40, 41)
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42. A perimeter sensing system comprising:
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a fiber interconnect cable; and fiber optic sensors positioned at different regions and connected by the fiber interconnect cable, each fiber optic sensor comprising; a sensing fiber that branches off the fiber interconnect cable, each sensing fiber having a free end not coupled to another fiber, the free end of the sensing fiber being coupled to a Faraday rotator mirror, and a filter to allow a light signal having a specific wavelength to pass to the sensing fiber and prevent light signals intended for other fiber optic sensors from passing to the sensing fiber, each fiber optic sensor generating an output light signal having the specific wavelength, the output light signal having a property that varies when stress is induced in the sensing fiber.
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43. A perimeter sensing system comprising:
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a fiber interconnect cable; and fiber optic sensors positioned at different regions and connected by the fiber interconnect cable, each fiber optic sensor comprising; a sensing fiber that branches off the fiber interconnect cable, and a filter to allow a light signal having a specific wavelength to pass to the sensing fiber and prevent light signals intended for other fiber optic sensors from passing to the sensing fiber, each fiber optic sensor generating an output light signal having the specific wavelength, the output light signal having a property that varies when stress is induced in the sensing fiber; wherein each of the filters comprises a first port for receiving light signals from an upstream segment of the fiber interconnect cable, a second port for sending light signals to the upstream segment of the fiber interconnect cable, a third port for sending light signals to a downstream segment of the fiber interconnect cable, and a fourth port for receiving light signals from the downstream segment of the fiber interconnect cable.
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Specification