節理式光纖光柵感測器之研發

Abstract

現今常用的地中滑動監測儀器有插入型傾斜儀、定置型傾斜儀、管式應變計和新發展的時域反射法(TDR)監測技術。而插入型傾斜儀由於量測方便、精度高所以使用最頻繁，但易受電磁波的影響。定置型傾斜儀雖然可自動化，但所費不貲。管式應變計由於使用應變片貼於管壁上，雖可自動化量測，但因線路龐大又電子訊號的互相干擾，往往影響量測精度。TDR利用電磁脈衝於同軸電纜中行進時，碰到截面變化而反射量測地層滑動，但同軸纜線之變形受到外部束制材料的影響而有所不同，進而影響到滑動量的反算。 本研究主要的目的是希望，利用光纖光柵感測系統單線多點感測及光纖傳輸不受電磁干擾等特性，發展出一套穩定、解析度高且量測深度不受限之儀器，若再搭配自動擷取以及預警系統，則可不分時間、地點，在危機發生之前立刻採取反應動作，降低災害的發生。本論文將闡述節理式光纖光柵感測器之發展以及現場測試結果。

The inclinometer probe (IP), in place inclinometer (IPI), pipe strain gage and the more recently developed time domain reflectometry (TDR) technique have been used as tools to monitor ground movement. IP with its advantages of convenience and high resolution is probably the most popular one. The pipe strain gage is made by attaching strain gages on a flexible pipe, can be automated, but is expensive to use. A large number of strain gages and thus signal cables are required in the pipe strain gage, it is likely to be interfered by the electromagnetic noise. TDR senses ground movement through distortion to a coaxial cable induced by the ground movement. The signal can be affected by the nature of the material surrounding the TDR cable. The objective of this reach is to take advantage of the unique capabilities of the fiber Bragg gratings and to develop a stable measurement system with sufficient resolution for ground movement monitoring purposes. When coupled with an automated data logger, the monitoring system is capable of providing early warning againstexcessive ground movement and prevent disasters. The thesis describes the development of this optic fiber grating segmented deflection monitoring probe and the result of its field applications.