On Friday, December 12, 2025, at 2:30 PM (CET), Giuseppe Cappelli will defend his doctoral thesis at the European Institute for Marine Studies (IUEM) in Brest, France.
Thesis Title: “Laser Reflectometry on Submarine Cables: Data Analysis on Laser Reflectometry (BOTDR and DAS) on Submarine Fiber Optic Cables and Recommendations for the Design and Construction of a New Generation of Hybrid Submarine Telecommunication Cables”
Abstract
Monitoring seafloor motion is essential for assessing seismic and tsunami hazards posed by submarine faults near coastal regions. However, direct offshore observations remain scarce due to the logistical challenges of deploying seafloor instruments. Distributed Fiber Optic Sensing (DFOS) offers a promising alternative by using the backscattered signal of laser light in optical fibers to measure strain, vibration, and temperature along their length.
This thesis investigates the sensitivity of the DFOS prototype FOCUS cable, deployed on a submarine fault offshore Catania, Italy, for seafloor strain monitoring using Brillouin Optical Time Domain Reflectometry (BOTDR) and Distributed Acoustic Sensing (DAS). The sensitivity of these techniques is affected by cable-seafloor coupling and strain transfer within the cable, which contains both loosely and tightly buffered fibers.
The cable’s response was analyzed through analytical modeling, laboratory tension tests, and field observations. Results show that fiber buffering alters the wavelength and amplitude of transmitted strain: the viscous gel in loosely buffered fibers significantly reduces strain transfer, while tightly buffered fibers preserve higher sensitivity.
Pullout tests in remolded seafloor sediments reveal that cable-seafloor interface shear strength depends on confining pressures and also impacts the reliability of external strain amplitude and wavelength detection.
Additionally, long-term BOTDR measurements in the Guadeloupe archipelago demonstrate the feasibility of monitoring seafloor temperature variations on existing submarine cables, opening new avenues for environmental and geophysical monitoring.
Keywords: Distributed Fiber Optic Sensing, Geodesy, Brillouin Optical Time Domain Reflectometry, Submarine Cables, Seismic Monitoring, DAS
How to attend
In person:
Amphithéâtre D, IUEM
Technopôle Brest-Iroise, Plouzané
Online:
Join via Zoom : https://cnrs.zoom.us/j/96236133233?pwd=rN8kra3iCm07mCoOFV2F8qMVvWFVP6.1
Jury Members
- Marc-André Gutscher, Research Director, Université de Bretagne Occidentale, Plouzané
- Yves Jaouen, Professor, Télécom Paris, Palaiseau
- Marcia Maia, Research Director, Université de Bretagne Occidentale, Plouzané
- Shane Murphy, Researcher, Ifremer Geo-Ocean, Plouzané
- Lionel Quetel, Engineer, IDIL Fibres Optiques, Lannion
- Diane Rivet, Assistant Professor, Université Côte d’Azur, GéoAzur, Nice
- Arantza Ugalde Aguirre, Researcher, CSIC, Spain
- Mark Zumberge, Researcher, University of California San Diego, United States
Invited Guests
- Philippe Jousset, Researcher, GFZ German Research Centre for Geosciences, Potsdam, Germany
- Stéphan Ker, Researcher, Ifremer Centre Bretagne, Plouzané
- Vincent Lanticq, Technical Director, FEBUS Optics, Pau
Conclusion
Giuseppe’s research represents a significant contribution to the field of submarine cable monitoring and opens new possibilities for leveraging existing telecommunications infrastructure for scientific purposes. The entire IDIL team congratulates Giuseppe on reaching this important milestone and wishes him success in his defense!
