CONDITION CHANGE MONITORING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a monitoring system for detecting a condition change such as a water level fluctuation due to a flood through a change of a back scattering light transmission loss distribution inside an optical fiber in each of multiple points for securing reliability even in occurrence of a failure in an optical fiber system. SOLUTION: In this condition change monitoring system having two systems of the optical fibers 3 and 3' and processing devices 1 and 1', the back scattering light transmission loss distribution of pulse light entered on the optical fibers 3 and 3' from processing devices 1 and 1' is measured for detecting a condition change such as the water level fluctuation in one point among the multiple points caused by increase of a bending loss by means of multiple sensors 4 arranged in the multiple points along the optical fibers 3 and 3'. The two systems of the optical fibers 3 and 3' are individually passed through sensors 4 doubly, so that detection and monitoring can be carried out in one system even when the other system breaks down, and consequently, the reliable monitoring system can be constructed.