Condition monitoring of railway tracks and vehicles using fibre optic sensing techniques

Although the European railway network has been expanded considerably within the last decade, monitoring of railway tracks and railway vehicles is still limited to epoch wise test drives or to local continuous measurements. In this contribution we report about new approaches to continuously monitor railway tracks and vehicles over tenths of kilometres using distributed fibre optic sensing (DFOS) techniques. In a first approach fibre optic strain sensing cables are attached to the railway tracks and strain changes due to rail deformations are depicted by distributed Brillouin measurements (BOTDA, BOFDA). These measurements allow the early detection of possible damages of the railway facilities due natural causes like mudflow, avalanches, floods, landslides and can prevent secondary damage by fast and correct counter actions. In a second approach we use optical communication cables which are commonly already laid next to modern rail infrastructure to detect flat spots in railway wheels. If these spots become too large they can damage train tracks and in extreme cases even cause derailment. In this contribution we demonstrate that distributed acoustic sensing (DAS) allows continuous monitoring of trains and to extract an individual profile that indicates flat spots. Since already laid communication cables are used no additional infrastructure is required apart from the optical time-domain reflectometry (OTDR) instrument. In our field installations in the Austrian railway network we demonstrate that BOFDA and OTDR systems complement each other to monitor incidents and deformations and thus enable permanent condition monitoring of railway tracks and vehicles over very long distances.