SPAIN: ADIF has signed an agreement for the Instituto Geográfico Nacional to use its optic fibre network to gather and analyse data about earthquakes, which are relatively common in the Iberian Peninsula.
To date, ADIF’s 16 000 km dark optic fibre network has not been made accessible to anyone outside the infrastructure manager. Under the four-year agreement, which may be extended to 2028, IGN will use various sections of the network for distributed acoustic sensing.
Interferometers will detect changes in the reflected intensity of the laser pulses sent through lengths of optic fibre of up to 50 km. Variations in the reflected intensity of successive pulses are caused by changes in the optical path length, due to either strain or temperature variations.
ADIF has been trialling DAS to monitor its infrastructure in a series of projects since 2007. The optic fibre laid alongside the railway acts as a sensor, enabling the monitoring of stresses in the track to a resolution of 10 m. In particular, DAS is being used as part of the Carril Roto 1 project to detect broken rails, and the Smanslope project to warn of rockfalls.