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The study on analysis of temperature effect of FBG optical fiber sensor introduced for long-term monitoring system

A steady technology development of such high-tech sensor system as optical fiber sensor, GPS sensor and laser sensor has led to increasingly utilizing them for monitoring the civil structure including the bridge. The state-of-the-art monitoring system making a great commitment to improving the stability and accuracy of the system has been effectively used for enhancing the efficiency of existing monitoring system. Optical fiber strain sensor, among those high-tech sensors, functions to measure the strain of the members using a contact method, like the existing strain sensor, because of the common characteristics of the strain sensors, but, compared to the existing electrical resistance strain sensor, it proved to be less affected by temperature as well as able to effectively correct the effect by temperature itself. The study, in an attempt to identify the temperature effect on FBG optical fiber strain sensor, among the sensors being used to monitoring system in bridges, evaluated the data from long-term measurement by real time monitoring system using optical fiber strain sensors. To that end, the real time monitoring system using optical fiber sensors were installed on Sapgyo Bridge (560m-long steel box girder composite bridge with maximum span of 80m) built in 1998 at Dang-jin, South Choong-chung Province and the monitoring continued for a certain period. The optical fiber sensors used was os310 of MOI (Micron Optic, Inc). The existing electrical resistance sensor was also set up under the same conditions for the purpose of comparing the temperature effect. In the wake of the analysis, the effect by temperature on measurement using optical fiber sensors under the condition of actual bridge could be identified.