Telecommunications Tunnel Monitoring System Employing BOTDR

摘要

We have developed a system for monitoring the state of telecommunications tunnels. This system detects deformation and damage by measuring the strain produced in the tunnels. Core components of the system are a Brillouin optical time-domain reflectometer (BOTDR), which allows distributed and long-distance strain measurement, and optical fiber sensors installed in tunnels. Basic performances of the system were confirmed by experiments in a laboratory. For example, the system can detect tunnel deformation with a measurement error of 0.1 mm from a contraction of 1 mm to an elongation of 5 mm over a span of 10 km. And earthquake resistance was confirmed. A system used in practice at present is introduced in detail.