CityDAS : Urban Monitoring Using Fiber Optics

Metropolitan areas need innovative tools to ensure continuous monitoring of their infrastructure and strengthen their resilience to climate change, natural hazards, and stresses related to human activities. Distributed Acoustic Sensing (DAS) technology, which leverages existing fiber-optic networks already deployed in urban environments (dark fiber), transforms these fibers into distributed sensors capable of measuring, in real time, the vibrations generated by traffic, infrastructure, and the ground, including in areas where the installation of conventional sensors is difficult.



Figure1



Figure 4 Station Grenoble
Within the CityDAS project (PUI funding), a first demonstrator is currently being deployed. It is based on a 12 km fiber-optic cable connecting the laboratory (with the support of DGDSI-DANET of Université Grenoble Alpes) to the Grenoble Alpes Métropole network, extending to Fontaine (Figure 1). Measurements are performed using an UPTECH SENSING DAS interrogator, made available for a four-week period. The selected configuration enables vibration measurements along the fiber using virtual sensors spaced every 2.5 m (approximately 5,000 virtual sensors), with a sampling frequency of 100 Hz, providing continuous, high-resolution monitoring of the urban environment.

In the longer term, the project aims to democratize the use of DAS by developing a platform for data visualization, management, and analysis, intended for local authorities, infrastructure managers, and the academic community. This platform will facilitate the monitoring of urban soils and infrastructure, contribute to the development of new scientific approaches for improving our understanding of seismic wave propagation in urban environments, and provide decision-support indicators to help guide public policies on resilience and sustainable territorial management.


During the testing period, the Venezuela earthquake occurred (magnitude 7.5 and 7.2 earthquakes, 200 km west of Caracas, on Wednesday, June 24, at 6:04 p.m. local time).



Figure 3 Stack and SignleTraces F(0.01,1)



The DAS system currently operating in Grenoble successfully recorded the seismic waves along its entire urban fiber path. The recordings (filtered between 0.01–0.3 Hz – Figure 2 – and 0.01–1 Hz – Figure 3) were compared with data acquired by the national seismic networks RAP (station OGSR, Saint-Roch Cemetery) and RLBP (station GRN, Mont Granier) (Figure 4), revealing excellent agreement between the recorded signals. Surface waves, as well as the resonance phenomena characteristic of the Grenoble basin (around 0.3–0.4 Hz), are clearly observed, demonstrating the potential of DAS for seismic monitoring in urban environments. These first observations open promising perspectives for monitoring the Grenoble basin, which is representative of Alpine valleys, as well as for imaging subsurface properties and characterizing the amplification of ground motion during earthquakes.


Figure 2 Stack and SignleTraces F(0.01,0.3)



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