Apparatus and method for fiber optic intrusion sensing
AssigneeThe Texas A&M University System
InventorsHenry F. Taylor, Chung E. Lee
Life of this patent
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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.
Claims35
Apparatus for sensing intrusion into a predefined perimeter, comprising:
- means for producing a plurality of coherent light pulses having a spectral width less than 0.1T.sub.1, where T.sub.1 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.
A method for sensing intrusion into a predefined perimeter, comprising the steps of:
- producing a coherent pulsed light having a spectral width less than 0.1T.sub.1, where T.sub.1 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.
Dependencies are inferred from the claim text.