Unattended ground sensor based on fiber Bragg grating technology

In this paper we have demonstrated an unattended seismic wave sensor based on the optical fiber Bragg grating (FBG) sensing technology. The basic principle of seismic wave detection and the fiber Bragg grating sensing technique is introduced in brief. Our FBG seismic sensor system consists of the broadband light source, FBG sensors coupled with spring / mass configuration, 3-dB optical couplers, demodulator FBG gratings, signal detection and processing hardware. Systematic experiments were carried out in Fort Dix at New Jersey. Target source includes personnel, military HMMWV and wheeled truck. The FFT analysis shows that the frequency response of the seismic signal is 20-40 Hz. The comparison data also show that the FBG sensor is more sensitive than the conventional seismic sensor both in personnel and vehicle detection. The ultimate object of this imbedded fiber optic sensor system is to recognize the presence of troop or vehicle movement through their induced seismic activity as a helpful tool in battlefield monitoring and perimeter defense system.