Sensitivity enhancement of long-gage FBG sensors for small macrostrain measurements

摘要

In our recent study,a structural health monitoring(SHM)strategy based on distributed fiber optic sensing techniques has been proposed to utilize the strain responses throughout the full or some partial areas of structures to detect the arbitrary and unforeseen damage.However,to perform this strategy more effectively,there is an increasing demand for improving the ability of such sensors to measure small responses especially concerning the cases like damage identification based on ambient vibration tests,fatigue crack monitoring of steel structures and crack detection for RC structures.This work puts forward a novel packaging design for long-gage fiber Bragg grating(FBG)sensors to enhance the measuring sensitivity for macrostrain responses.The basic idea is to utilize two materials of different stiffness to package the optical fiber and impose the deformation within the gauge length largely on the essential sensing FBG part.A series of tests are carried out to verify the ability of the improved sensor to detect the small crack and measure the slight vibration.By compared with the measurements from the pristine FBG sensor,the influence of environmental noise on those from the novel one is discussed as well.