Distributed Fiber-Optic OTDR-Based Intrusion Sensor System Using Actively Q-Switched Ring Laser

• Main Authors: Lee, Yueh-Feng, 李岳峯
• Other Authors: Wang, Li-Karn
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/7pq8hm

碩士 === 國立清華大學 === 光電工程研究所 === 106 === In this paper, we use a pulse laser, formed by incorporating a Mach-Zehnder interferometer in a ring resonator of a fiber laser, and launch the pulse into an 8.8 kilometer bare fiber, to detect backward Rayleigh scattering. The Mach-Zehnder interferometer is very sensitive to the phase difference caused by the perturbation on the fiber. So when it is destructive interference, it means there is no power in the cavity. On the contrary, there will be lots of energy when constructive interference occurs. Backward Rayleigh scattering is also sensitive to the phase difference caused by the perturbation on the fiber. So it means that when there is a phase difference caused by the perturbation on the fiber, the power of backward Rayleigh scattering would change. We can then determine whether the fiber is bent or vibrated by inspecting the power variation of the backward Rayleigh scattering. So this system can be used for security of perimeter zones.