Fiber-reinforced polymer-packaged optical fiber sensors based on Brillouin optical time-domain analysis

Abstract

Brillouin optical time-domain reflectometry (BOTDR) and Brillouin optical time-domain analysis (BOTDA) are considered to be promising and practical sensing techniques for large structures. However, there is still a major obstacle to applying BOTDR or BOTDA on large-scales; the high cost and unreliability associated with sensor installation and failure. We report a novel, low-cost, and highly reliable BOTD sensor using a rebar consisting of a bare optical fiber (OF) packaged in fiber-reinforced polymer (FRP) and named BOTD-FRP-OF. We investigate the surface bonding and its mechanical strength scanning-electron-microscope and intensity experiments. Considering the strain difference between OF and host matrix, which may result in measurement error, the strain transfer from host to OF has been studied theoretically. Furthermore, the sensing properties of glass FRP-OFs for strain and temperature at different gauge lengths were tested under different spatial and readout resolutions using commercial BOTDA. Finally, an absolute dual-BOTD-FRP-OF temperature compensation method is proposed and has been tested. This novel FRP-OF rebar shows both high strength and good sensing properties, which can be used in long-term structural health monitoring for civil infrastructure.