Monitoring Large Railways Infrastructures Using Hybrid Optical Fibers Sensor Systems

In this paper we propose a hybrid fiber optics sensor system, based on Fiber Bragg Gratings (FBG) and Raman distributed temperature sensing (RDTS), for monitoring essential sites within large railway infrastructures like bridges, viaducts and slopes potentially subject to landslides. The geometrical rail track condition is monitored in real-time using fiber optic sensors, providing early warning if pre-defined thresholds are exceeded in terms of longitudinal, horizontal and cross-level defects. The sensor reading units can be remotely located from the monitored zones, without requiring active elements on the tracks and ensuring high immunity to electromagnetic interference. The proposed technology has been first validated in railway laboratories and then in field trials confirming its capability to detect defects over pre-established thresholds and the absence of false alarms with regular train circulation.