Fiber Sensors for Strain Measurements and Axle Counting in High-Speed Railway Applications

High-speed railway systems have begun to be widely deployed. To meet increasingly stringent requirements under harsh running environments, we propose and demonstrate three fiber-Bragg-grating (FBG)-based approaches for the strain measurement and axle counting in high-speed railway systems, including matched gratings, grating under uneven strain distribution, and semi-free grating. All approaches are laboratory verified and evaluated using the train load platform. Pros and cons are also discussed in terms of feasibility and cost-effectiveness.