Intrusion detection system for use on an optical fiber using a translator of transmitted data for optimum monitoring conditions
First Claim
1. A method of detecting intrusion into a multimode optical fiber comprising:
- launching a light signal into a proximal end of the optical fiber from a source of light that is offset from the center of a core of the optical fiber so as to establish a non-uniform made field power distribution in the optical fiber;
using a tap coupler at a distal end of the optical fiber to capture a portion only of the light signal arriving at a the distal end of the cable, the portion containing only higher order signal modes;
monitoring the portion for transient changes in the portion that are characteristic of cable handling; and
activating an alarm in response to detection of said transient changes.
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Accused Products
Abstract
A method and system of intrusion detection system for a multimode fiber optic cable. A light signal is launched into the cable fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the cable. A small portion of the higher order signal modes arriving at the remote end of the cable is sampled by use of a coupler and monitored for transient changes in the mode field power distribution. The power distribution changes with physical disturbance of the cable. When those changes are detected as being characteristic of fiber intrusion, the system activates an alarm. This method can sense and alarm any attempt to access the optical fibers in a fiber optic communication cable. In preferred embodiments, the active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion. A translator can be provided in an existing optical fiber system in which the data signals are translated in wavelength and/or launch conditions to optimize the monitoring signals in an otherwise non-optimized system.
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Citations
13 Claims
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1. A method of detecting intrusion into a multimode optical fiber comprising:
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launching a light signal into a proximal end of the optical fiber from a source of light that is offset from the center of a core of the optical fiber so as to establish a non-uniform made field power distribution in the optical fiber; using a tap coupler at a distal end of the optical fiber to capture a portion only of the light signal arriving at a the distal end of the cable, the portion containing only higher order signal modes; monitoring the portion for transient changes in the portion that are characteristic of cable handling; and activating an alarm in response to detection of said transient changes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of detecting intrusion into a multimode optical fiber comprising:
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launching a light signal into a proximal end of the optical fiber from a source of light that is offset from the center of a core of the optical fiber so as to establish a non-uniform mode field power distribution in the optical fiber; using a tap coupler at a distal end of the optical fiber to capture a portion only of the light signal arriving at the distal end of the cable, the portion containing only higher order signal modes; monitoring the portion for transient changes in the portion that are characteristic of cable handling; activating an alarm in response to detection of said transient changes that are characteristic of handling of the fiber; wherein the tap coupler taps off the portion of the higher order modes and provides a larger separate signal for forming a bulk optical launch distribution; wherein the larger separate signal is delivered to a detector circuit where an absolute throughput power of the launched light signal is calculated therefrom; using a significant change in the portion and the absolute throughput power of the larger separate signal to indicate a problem with the source or the optical fiber; and using a transient and steady state change in the optical power of the portion only to provide an indication of an intrusion attempt.
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12. A method of detecting intrusion into a multimode optical fiber comprising:
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launching a light signal into a proximal end of the optical fiber from a source of light that is offset from the center of a core of the optical fiber so as to establish a non-uniform mode field power distribution in the optical fiber; capturing higher order signal modes only of the light signal arriving at the distal end of the cable, the portion containing only higher order signal modes; monitoring over time a value of the optical power of the higher order signal modes for transient changes in the optical power of the higher order signal modes; and activating an alarm in response to detection of said transient changes that are characteristic of cable handling.
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13. A method of detecting intrusion into a multimode optical fiber comprising:
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launching a light signal into a proximal end of the optical fiber from a source of light that is offset from the center of a core of the optical fiber so as to establish a non-uniform mode field power distribution in the optical fiber; using a tap coupler at a distal end of the optical fiber to capture a portion only of the light signal arriving at the distal end of the cable, the portion containing only higher order signal modes; monitoring over time a value of the optical power of the higher order signal modes for transient changes in the optical power of the higher order signal modes; and activating an alarm in response to detection of said transient changes that are characteristic of cable handling.
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Specification