Real-time Measurements of Water Level and Temperature using Fiber-optic Sensors Based on an OTDR

In this study, two fiber-optic sensors were fabricated to measure water level and temperature using optical fibers, a coupler, a Lophine and an OTDR (optical time-domain reflectometer). First, using Fresnel's reflection generated at the distal-ends of each optical fiber, which was installed at different depth, we measured the water level according to the variation of water level. Next, we also measured the temperature of water using a temperature sensing probe based on the Lophine, whose absorbance changes with the temperature. The measurable temperature range of the fiber-optic sensor is from 5℃ to 65℃ because the maximum operation temperature of the optical fiber without a physical deterioration is up to 80℃.