基于弱光栅阵列技术和相位敏感光时域反射仪(Φ-OTDR)设计了一种低成本大长周界安防系统。系统利用光栅位置和时分复用技术实现对振动点的定位,依据光栅反射的回光与其两侧光纤的背向瑞利散射光相干涉的原理,解调得到的振动信号信噪比约为30 dB。使用光栅间距为5 m的光缆进行频率为10~90 Hz的振动解调测试,解调结果显示,系统具有优秀的频率响应特性。同时,对周界安防报警系统的报警算法进行了测试,测试结果表明,该系统的误报率在10%以内,漏报率为0。此系统探测长度可达50 km,远长于现有的光纤周界产品,而且解调方式简单、成本较低,具有广阔的应用前景。

In this study, we design a low-cost and long-perimeter security system using the weak grating array technology and phase-sensitive optical time domain reflectometer. The developed system uses the grating positions and the time-division multiplexing technique to precisely locate the external vibration points. The signal-to-noise ratio of the demodulated vibration signal is approximately 30 dB according to the principle of interference between the reflected light of the grating and the back Rayleigh scattering light of the two sides of the fiber. Herein, we use a fiber optic cable with a 5-m grating spacing to demodulate the vibration having a frequency of 10--90 Hz, and the demodulated results prove the excellent frequency response characteristics of the system. Meanwhile, the alarm algorithm of the proposed perimeter security alarm system is verified. The test results prove that the false alarm rate of the system is less than 10% and that the missing alarm rate is 0. The developed system has a maximum detection length of 50 km, which is considerably larger than those of the existing optical fiber perimeter products, and the demodulation method is simple and cheap; therefore, it has a broad application potential.