Multi-Component DAS Sensing

The project of Simone Probst explores new ways to extract directional information from Distributed Acoustic Sensing (DAS) measurements by shaping fiber-optic cables into circular loops. Unlike straight-line DAS, which is primarily sensitive to axial strain along the fiber direction, loop geometries provide sensitivity to different azimuthal components of the wavefield. By deploying three loops perpendicular to each other, we create a small fiber-optic "sphere" sensor, sensitive to the full strain tensor (Figure 1).  

A key enabler of this approach is a novel high-resolution DAS interrogator - developed by Sensiphi -which achieves a 20 cm gauge length operating with custom ULEB fiber, as tested in the CIWE lab. This short gauge length allows us to use loops with relatively small diameters while still resolving the multiple strain components. 

A first set of field data using both a full "sphere" configuration as well as individual loop sensors has been acquired, with both the high-resolution and conventional DAS system. The initial recordings are promising and clearly show directional sensitivity. Ongoing work focuses on extracting the individual strain components from these datasets and on improving the robustness and accuracy of the component extraction. 

The SNSF funded project is hosted in the ETHZ MGE group led by Johan Robertsson, with main collaborators Pascal Edme and Fredrik Andersson.