Apparatus and method for fiber optic intrusion sensing
First Claim
1. Apparatus for sensing intrusion into a predefined perimeter, comprising:
- means for producing a plurality of coherent light pulses having a spectral width less than 0.1T1, where T1 is the width of each coherent light pulse;
an optical sensing fiber having a first predetermined length receiving at least a portion of said plurality of coherent light pulses and being positioned along said predefined perimeter, said optical sensing fiber producing a backscattered light in response to receiving said plurality of coherent light pulses;
an optical receiving fiber arranged to receive said backscattered light from said optical sensing fiber; and
detecting means coupled to said optical receiving fiber for receiving said backscattered light and producing a signal indicative of an intrusion in response to a perturbation in said backscattered light.
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Abstract
Apparatus for sensing intrusion into a predefined perimeter comprises means for producing a coherent pulsed light, which is injected into an optical sensing fiber having a first predetermined length and positioned along the predefined perimeter. A backscattered light in response to receiving the coherent light pulses is produced and coupled into an optical receiving fiber. The backscattered light is detected by a photodetector and a signal indicative of the backscattered light is produced. An intrusion is detectable from the produced signal as indicated by a change in the backscattered light. To increase the sensitivity of the apparatus, a reference fiber and an interferometer may also be employed.
304 Citations
35 Claims
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1. Apparatus for sensing intrusion into a predefined perimeter, comprising:
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means for producing a plurality of coherent light pulses having a spectral width less than 0.1T1, where T1 is the width of each coherent light pulse; an optical sensing fiber having a first predetermined length receiving at least a portion of said plurality of coherent light pulses and being positioned along said predefined perimeter, said optical sensing fiber producing a backscattered light in response to receiving said plurality of coherent light pulses; an optical receiving fiber arranged to receive said backscattered light from said optical sensing fiber; and detecting means coupled to said optical receiving fiber for receiving said backscattered light and producing a signal indicative of an intrusion in response to a perturbation in said backscattered light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method for sensing intrusion into a predefined perimeter, comprising the steps of:
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producing a coherent pulsed light having a spectral width less than 0.1T1, where T1 is the width of each coherent light pulse; injecting at least a portion of said coherent pulsed light into an optical sensing fiber having a first predetermined length and positioned along said predefined perimeter; producing a backscattered light in response to receiving said coherent pulsed light; and receiving said backscattered light from said optical sensing fiber and producing a signal indicative of an intrusion in response to a perturbation in said backscattered light. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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Specification