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Proceedings Paper

Distributed fiber optic intrusion sensor system for monitoring long perimeters
Author(s): Juan C. Juarez; Henry F. Taylor
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Paper Abstract

The use of an optical fiber as a distributed sensor for detecting and locating intruders over long perimeters (>10 km) is described. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer (Φ-OTDR). Light pulses from a cw laser operating in a single longitudinal mode and with low (MHz/min range) frequency drift are injected into one end of the single mode fiber, and the backscattered light is monitored with a photodetector. In laboratory tests with 12 km of fiber on reels, the effects of localized phase perturbations induced by a piezoelectric fiber stretcher on Φ-OTDR traces were characterized. In field tests in which the sensing element is a single mode fiber in a 3-mm diameter cable buried in a 20-46 cm deep, 10 cm wide trench in clay soil, detection of intruders on foot up to 4.6 m from the cable line was achieved. In desert terrain field tests in which the sensing fiber is in a 4.5-mm diameter cable buried in a 30 cm deep, 75 cm wide trench filled with loose sand, high sensitivity and consistent detection of intruders on foot and of vehicles traveling down a road near the cable line was realized over a cable length of 8.5 km and a total fiber path of 19 km. Based on these results, this technology may be regarded as a candidate for providing low-cost perimeter security for nuclear power plants, electrical power distribution centers, storage facilities for fuel and volatile chemicals, communication hubs, airports, government offices, military bases, embassies, and national borders.

Paper Details

Date Published: 20 May 2005
PDF: 12 pages
Proc. SPIE 5778, Sensors, and Command, Control, Communications, and Intelligence (C3I) Technologies for Homeland Security and Homeland Defense IV, (20 May 2005); doi: 10.1117/12.602638
Show Author Affiliations
Juan C. Juarez, Texas A&M Univ. (United States)
Henry F. Taylor, Texas A&M Univ. (United States)


Published in SPIE Proceedings Vol. 5778:
Sensors, and Command, Control, Communications, and Intelligence (C3I) Technologies for Homeland Security and Homeland Defense IV
Edward M. Carapezza, Editor(s)

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