Development of highly sensitive optical fiber sensor system for wide-area disaster prevention

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The purpose of the research is to develop a new optical fiber sensor system for sensing and collecting remote information of strain, temperature and earthquake amplitude of architectures in wide area The Bragg grating Doer sensor was fabricated and a new strain analyzing system was developed fir practical use in various applications.(1) Fabrication of FBG fiber sensors using the ultra-short pulsed laser The Bragg grating sensor has been inscribed in the single-mode silica fiber by using a Ti: Sapphire mode-locked laser system with 150 fs duration. Point-by-point method was applied and a reflection of -25db was obtained in 1550 nm wavelength spectrum. The sensors are designed for use of the FBG-OTDR sensing system.(2) Development of FBG-OTDR sensing system for strain and temperature measurement.A new sensing system called FBG-OTDR scheme has been developed fir sensing a position and magnitude of strain of the FBG sensors. Accuracy of the strain measurement is 5x10^<-6> with sensor spatial resolution of 15cm for maximum distance over 30km and temperature range of 0〜500 degree C in lms time resolution.(3) Extremely multi-point sensing capabilityBy using low reflectivity FBG sensors, multi-point sensors can be distributed in a single fiber with 1,000 points in this system and can be extended over several 10_4 FBG sensors in the modified system. The system has potential for low-cost practice sensing of wide-area artificial structures for prevention of disaster.