Development and application of displacement-strain based integrated fiber optic sensor system for multiplexing and multi-parameter measurement in structural health monitoring

Abstract

Civil engineering structure health and usage monitoring systems (HUMS) are being developed to pre-vent unexpected accidents and to replace conventional maintenance services. In order to perform HUMS successfully in real applications, various sensors are installed at critical points of large size structures to moni-tor and diagnose the conditions of the structures. However, there are some disadvantages for the conven-tional electric-based sensors such as the addition of mass, wiring problems, and EMI (electromagnetic inter-ference). Thus, optical fiber-based sensors are being studied to overcome such existing problems of the conven-tional electric-based sensors. However, although the conventional optical fiber-based sensing systems are suitable for multiplexing, it presents still difficulties in performing multi-parameter measurements simultane-ously with multiplexing. Moreover, with the lack of an integrated system for multi-parameter measurement, various kinds of equipment are necessary, hence resulting in the critical problem of added weight to the struc-tures. To guarantee the accuracy and reliability of HUMSs in real applications, strain-displacement based multiplexing and multi-parameter measurements using integrated optical sensor systems are presented and developed in this study. First of all, two novel sensor principles are presented in order to resolve limitations in installation and complex cabling problems of the conventional transmission type grating based fiber optic sensors. The first sensor principle was realized using a reflective grating panel after investigation of the sensor signal characteristics according to the grating panel pattern. Based on the first sensor principle, a fiber optic accelerometer prototype was fabricated and investigated. Furthermore, in order to realize the proposed sensor principle as an accelerometer, a single degree of freedom system is developed. The appropriate leaf spring pattern is investigated for high sensitiv...