LOKI: A Field-Proven Optical Interrogator for High-Precision Remote Point Sensing of Electronics-Free Sensors, Now Available to the Geoscientific Community

LOKI is an optical interrogator initially developed by ESEO and subsequently refined over several generations of prototypes. Over the past five years, these prototypes have been deployed worldwide in partnership with IPGP to investigate a wide range of sensor modalities (volcano monitoring, underwater seismicity, geothermal activity…), demonstrating robust field performance and highlighting new opportunities for high-precision measurements.

Technically, LOKI enables electronic-less point-based measurements at the end of long optical fibers (up to 30 km). This capability facilitates deployments under the sea or atop volcanoes, with LOKI situated onshore or in a distant safe area. Furthermore, it complements distributed acoustic sensing (DAS) systems that provide measurements along the fiber’s length. The combination of distributed (DAS) and pointwise (LOKI) approaches offers flexibility for complex experimental setups, enabling broad spatial coverage and locally detailed monitoring.

The presentation will outline various field campaigns and application scenarios where LOKI has been successfully deployed. Notably, LOKI can operate as part of an autonomous station in harsh outdoor environments, requiring only 6 W from a solar panel. The sensing elements employed in these deployments are fully optical and maintenance-free, including all-fiber strainmeters and seismometers, with additional modalities under development, including rotational seismometer. Retrofitting existing seismometers to operate them with optical readout will also be discussed, demonstrating how LOKI enables remote interrogation and broadened research possibilities.

From now on, LOKI is industrially manufactured by MAÅGM, ensuring consistent performance and readiness for extensive deployment, with dedicated support and maintenance services. This communication aims to share insights gained from diverse field tests and to inform the scientific community that these experiments are now reproducible and accessible, opening new avenues of research in seismic and structural monitoring.