Intrusion detection and classification using optical fiber vibration sensor

In this paper, the design of a perimeter security system based on fiber optic disturbance sensor with improved sensitivity was described. The system consisted of fiber optic disturbance sensor that was the Sagnac interferometer and a control computer. First, the light polarization and fiber birefringence effects on the sensor sensitivity improvement were studied. Then a modified digital Phase Generated Carrier (PGC) demodulation technique was used to eliminate phase drifts in the interferometric sensor. A prototype system with 40 m sensing cable was constructed and tested. The sensing cable was buried along the boundaries of the protected area to detect disturbance generated by intruders. The test result verified that this sensor was very sensitive to intrusion behavior and was also able to classify and discriminate between different intrusion and non-intrusion events.