Ho Hsin-Ren, Hsieh Cheng-Yu, Hsu Yung-Cheng, Wang Likarn
Opt Express. 2021 Oct 11;29(21):34341-34359. doi: 10.1364/OE.438276.
A new type of dual Mach-Zehnder interferometer (DMZI) scheme is presented to eliminate the polarization induced fading usually encountered in fiber-optic intrusion detection systems that use DMZIs. With such a new optical scheme, two identical signal waveforms with only a time delay that corresponds to the location of intrusion can always be obtained without using a polarization control loop. In the study, we also present a new algorithm for locating the intrusion-induced disturbance on the fiber. The experiments carried out in our lab have demonstrated that locating errors of <26 m can be obtained with the presented system used for detecting an intrusion point on a 250 meter long fiber cable. Also, the proposed DMZI system has been tested for years without changing any optical components except the laser type and the length of the sensing fiber. Notably, the thresholds for determining the intrusion have never been altered since the laser type was changed in 2018. In addition, detections of the clockwise and counter-clockwise signals have maintained a condition of high interference visibility, and the locating capability has remained at the same level.
提出了一种新型双马赫-曾德尔干涉仪（DMZI）方案，以消除在使用DMZI的光纤入侵检测系统中通常遇到的偏振引起的衰落。采用这种新的光学方案，无需使用偏振控制环，总能获得两个仅存在对应于入侵位置的时间延迟的相同信号波形。在本研究中，我们还提出了一种用于定位光纤上入侵引起的干扰的新算法。在我们实验室进行的实验表明，使用所提出的系统检测250米长光纤电缆上的入侵点时，定位误差可小于26米。此外，除了激光类型和传感光纤长度外，所提出的DMZI系统已经经过多年测试，未更换任何光学组件。值得注意的是，自2018年更换激光类型以来，确定入侵的阈值从未改变。此外，顺时针和逆时针信号的检测一直保持着高干涉可见度的状态，并且定位能力一直保持在同一水平。
