Application of distributed sensing technique with FBG sensors to structural health monitoring

We have developed a new distributed strain measurement system with a long gauge Fiber Bragg Grating (FBG) sensor based on Optical Frequency Domain Reflectometry (OFDR), which enables us to measure strain at an arbitrary position along the FBG sensor with the high spatial resolution. In this study, to evaluate the performance and characteristics of this system, we built the simulation model of the system using the transfer matrix method based on coupled mode theory. By the simulated results, we confirmed that the spatial resolution of the system was less than I mm. Furthermore, as examples of application to SHM, we implemented two experiments. In these experiments, we could successfully measure the strain distributions in specimens with the high spatial resolution and it showed the good agreement of the results between the simulation and experiment. These results also show that this distributed sensing technique with the high spatial resolution can be applied to damage detection and assessment of the structural integrity.