Integration and Application of a Fiber-Optic Sensing System for Monitoring Debris Flows

This study presents an innovative fiber-optic sensing system for monitoring debris flows. The system mainly comprises an interrogator and four fiber Bragg grating accelerometers. The field tests show that signal-to-noise-ratio (SNR) of the fiber-optic sensor is 10 dB higher than that of a geophone. Following confirmation of the reliability of the proposed sensing system, the systems are deployed along the Ai-Yu-Zi and Chu-Shui Creeks in Nautou County, Taiwan, for monitoring debris flows. The four accelerometers are installed in series. The systems have detected several debris flows in 2012. The monitored data reveal that the frequency range of the acceleration of ground vibration is 10-150 Hz, which is the same as that of the velocity of ground vibration detected by a sensing system that includes geophones. Because the fiber-optic sensing system is more sensitive than the geophone system, the proposed fiber-optic sensing system is highly promising for use in monitoring natural disasters that generate ground vibrations.本研究藉由組合光纖光柵加速度計、解調儀、及其他相關元件，發展一套可偵測土 石流之光纖感測系統。現地測試結果顯示，與目前常用含地聲檢知器的土石流感測系統相較， 本系統所測得地表振動訊號之訊雜比比前者高10 dB。在測試系統量測效能後，將此系統分別 架設於南投縣信義鄉神木村之愛玉子溪及出水溪上。系統中採串連方式配置四個光纖加速度 計，並於2012 年監測到多場土石流。觀測結果顯示，光纖感測系統所測得土石流所造成地表 振動之加速度，與過去地聲檢知器所測得土石流地表振動速度，兩者頻率一樣，均為10–150 Hz。由於光纖光柵加速度計相較於地聲檢知器更為靈敏，因此，除了可應用於偵測土石流外， 也可應用於監測會產生地表振動的其他坡地災害，如：落石及山崩等