Distributed fibre optic sensing as a versatile monitoring tool for modern societies

Distributed fibre optic sensing (DFOS) is using one or a combination of the three available physical backscattering phenomena, namely Rayleigh, Brillouin, and Raman, to provide full length coverage at meter scale of vibration, temperature and strain measurements. The fibre optic cable (FOC) is the sensing medium. Its robustness, flexibility, and low loss together with its insensitivity to any electro-magnetic perturbation makes it a unique tool for sensing in modern urban societies.

Temperature (DTS) and acoustic (DAS) measurements are deployed onshore and offshore for power cable monitoring. Offshore, the DTS temperature signal is used to dynamically handle the load, detect potentially damaging hot spots and assess cable deburial. As a by-product, it gives information on the seabed mobility and on the ocean bottom temperature. Both offshore and on land, the DAS acoustic information provides almost instantaneous cable fault position, thus shortening power cut from usually many months to a few weeks. In addition, it provides information on waves, traffic, and seismic activity.

Strain (DSS) measurements are used for structural health monitoring (SHM), looking at tunnels, bridges, dam, in view of preventing potential failures. DSS can also be used along pipeline right of way in challenging terrains for early detection of geohazard that may result in massive landslide and ultimately in pipeline rupture.

The DFOS value for the society is not so much in its capacity to measure, but in the information that it provides on an asset so that meaningful decisions can be taken. Thus, it is not the backscattering that matters but the application understanding and the data software processing which become key to the deployment and efficiency of fibre-based monitoring. For instance, it is the DTS driven finite element modelling of heat propagation in the seabed that provides the depth of burial estimation. Likewise, it is the complex machine learning based DAS processing that provides intrusion detection.

Based on years of field data, using all the DFOS principles and the associated software, we will show how DFOS is being used in modern societies and what valuable data can be extracted from the asset.