Great discussions and insightful talks at theThe LOKI remote optical interrogator was presented, showcasing its great potential for various types of instruments to monitor underwater seismicity. The poster session, held in a historic library, was truly inspiring. Always a pleasure to spend a day with passionate scientists, sharing their discoveries and the methods behind them. Looking forward to contributing even more, thanks to the instruments we are developing and offering!
Thank you co-authors and P.Bernard (IPGP) for being there.
EseoPhilippe MenardHeiner IgelFranck T.
https://lnkd.in/eT7BJrj4

 

Frédéric Guattari1, Hippolyte Dupont1, Pascal Bernard2, Philipe Ménard3, Romain Ferron3, Mathieu Feuilloy3, Guy Plantier3, Felix Bernauer4, Heiner Igel4, Wayne Crawford2, Celine Hadziioannou5, Jean-Philippe Métaxian2

  1. MAÅGM, Le Mans, France
  2. Institut de Physique du Globe de Paris (IPGP) , Université Paris Cité, Paris, France
  3. Ecole Supérieure d’Electricité de l’Ouest (ESEO), France
  4. Ludwig Maximilian Universität (LMU), Germany
  5. University of Hamburg, Germany

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

Technically, LOKI enables electronics-free, point-based measurements at the end of long optical fibers (up to 30 km, with plans for further extension). This capability facilitates underwater deployment, with LOKI located onshore or on a buoy to provide real-time data acquisition.

Furthermore, LOKI can complement distributed acoustic sensing (DAS) systems, which provide measurements along the fiber’s entire length. By combining distributed (DAS) and pointwise (LOKI) approaches, researchers can achieve both broad spatial coverage and highly detailed local monitoring—ideal for complex experimental setups.

The presentation will outline various field campaigns and application scenarios where LOKI has been successfully deployed, in particular the installation of a passive optical 3-component ocean-bottom seismometer offshore Les Saintes Islands, Guadeloupe, as well as its forthcoming use by IPGP at Petras ‘on-buoy’ next year.

A special focus will illustrate the potential of underwater rotational monitoring, as LOKI can enable such instrumentation within a 6C seismometer at the ocean bottom. By measuring spatial wavefield gradients, a 6C station could, in principle, replace multiple seismic sensors. A high-performance 6C ocean-bottom seismometer would also refine noise characterization and enhance data quality. Improved anisotropy estimation, single-station wave-type fingerprinting, source direction finding, dynamic tilt correction, and shallow 1D velocity inversion are among the most promising 6C applications.

LOKI is now industrially manufactured by MAÅGM, ensuring consistent performance and readiness for large-scale deployment, supported by dedicated maintenance services. This communication aims to showcase the significant potential of this optical technology and to inform the scientific community that these experiments are now both reproducible and accessible—opening new avenues in underwater monitoring research.