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Fiber Bragg grating system for continuous large-scale monitoring of convergence in Rossio Tunnel

On this paper, the implemented solution for continuous monitoring of Rossio Train Tunnel in Lisbon (Portugal) is described. The monitoring system is a complete solution that comprises measurements of strain and temperature with more than 850 fiber Bragg grating sensors, data acquisition, processing, storage and easy access through a web platform. The applied sensing technology has several advantages such as fiber Bragg sensors being immune to electrical interferences and suited to harsh environments. The used method for convergence monitoring (MEMCOT) makes it possible to determine tunnel convergences based on strain measurements around the tunnel contour. An optoelectronic measurement unit and optical switch are deployed at the entrance of the tunnel and remotely connected to a server that saves and displays information to authorized users in web interface.