Field test of a distributed fiber-optic intrusion sensor system for long perimeters

Area of Science:

• Optoelectronics
• Fiber optic sensing
• Security systems

Background:

• Distributed sensor systems are crucial for perimeter security.
• Phase-sensitive optical time-domain reflectometry (phi-OTDR) offers high sensitivity for detecting disturbances.
• Desert environments present unique challenges for sensor deployment and performance.

Purpose of the Study:

• To evaluate the effectiveness of a phi-OTDR based distributed sensor system for intruder detection in desert terrain.
• To assess the system's performance over extended fiber lengths and varying environmental conditions.
• To demonstrate real-time detection and localization capabilities.

Main Methods:

• Utilized a single-mode telecommunications fiber optic cable buried in sand as the sensing element.
• Employed a continuous-wave Er:fiber Fabry-Perot laser for signal injection.
• Monitored orthogonal polarizations of backscattered light with separate receivers.
• Implemented a trace subtraction method to detect localized phase changes.

Main Results:

• Achieved high sensitivity and consistent detection of both foot traffic and vehicles.
• Successfully operated the system over an 8.5 km cable length (19 km total fiber path).
• Demonstrated real-time intruder detection and localization capabilities in desert conditions.

Conclusions:

• The phi-OTDR distributed sensor system is a viable and effective solution for perimeter security in challenging desert environments.
• The system's ability to detect diverse threats in real-time validates its practical application.
• Buried fiber optic sensing provides a robust method for long-range surveillance.