为了对长距离周界入侵进行定位, 提出一种使用3×3耦合器作为基本元件的Fox-Smith干涉仪光纤入侵探测系统。对此结构及其定位方法进行了理论分析和实验验证。当有冲击作用在传感光纤上时, 光纤中的光波受到相位调制, 利用两束光波受到调制的时间不同从而产生相位差;通过对解调出的相位信号进行傅里叶变换, 获取了一系列的陷波点。结果表明,在长度为34.793km传感光纤上, 获得平均定位误差为±83m, 可见该种结构在长距离周界系统定位是可行的。这一结果在长距离周界入侵定位上具有一定的帮助。

In order to locate the long distance perimeter intrusion, an optical fiber intrusion detection system was promoted based on Fox-Smith interferometer with 3×3 coupler as the main component. Theoretical analysis and experimental verification were carried out on the system and its location method. When the impact force acts on the sensor fiber, the optical wave is modulated by the phase. There is phase difference because of the modulation time difference between both the beams. A series of trap points are gained after the fast Fourier transform of the demodulated phase signal. The results showed the average location error was ±83m when the length of sensing fiber was 34.793km.The system is feasible for long intrusion location and helpful to intrusion detection.