Ultra-long Optical Fiber Fence Alarm System Based On FBG Sensors

Fiber fence is a kind of sensing system using optical fiber as a sensing medium, which can be divided into distributed system and quasi-distributed system. Fiber fence is based on distributed optical fiber sensing technology and a variety of fiber-optic sensors. Comparing with the traditional fence alarm system, fiber fence has a series of advantages, such as anti-electromagnetic interference, anti-corrosion, anti-radiation, low loss, wide range and easy to concealment. In this paper, a fiber-optic fence sensor alarm system was researched based on Fiber Bragg Grating (FBG), which is a quasi-distributed sensing system. This system has capability to monitor the unexpected invasion events in real-time and remote at the field of security monitoring. Based on FBG sensors, the author has made much effort on research of the fiber-optic fence sensor alarm system, the main works as following three aspects: signal processing of the system, ultra-long haul fiber-optic fence alarm system technology research and software design.First of all, the development of domestic and international fiber-optic fence technical is introduced, and the FBG sensor multiplexing and demodulation techniques is analyzed. An experimental model is set up to acquire the alarm signal and processing the signal. The dynamic margin denoising and wavelet denoising method are applied to reduce the alarm signal noise, empirical mode decomposition (EMD) and the characteristics of wavelet packet entropy algorithm are constituted to solve the locating problem of alarm signal. Invasion signal characteristics and seven invasion patterns can be distinguished by this system.Then, a variety of optical amplification technology and long-distance FBG sensor system are discussed. Ultra-long fiber-optic fence demodulation with TDM and OTDR technology is proposed, and ultra-long fiber-optic fence system with 150 km fiber based on erbium-doped fiber amplifier (EDFA) amplification is achieved; then a optical amplification program based on EDFA and fiber Raman amplifiers (FRA) is proposed to achieve the 275km ultra-long haul optical FBG fence systems with SNR of 27.5dB ; in order to optimize the system further, the FBG sensor system based on Bi-directional Raman lossless transmission system has been proposed.Finally, fiber-optic fence alarm system software based on the LabVIEW programming language is designed. The software flow chart of the program is designed; the signal acquisition module and a variety of signal processing module are composed to achieve the basic functions of alarm software; a software interface is designed, and can show intuitive signal vividly; the effective of the software is proved by experiment.