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Contributing to the detection of the most energetic neutrino ever observed!
October 6, 2025
For over a decade, Exail has brought its expertise in underwater acoustics and photonic integrated systems to the KM3NeT project: a European telescope placed on the seafloor of the Mediterranean Sea, designed to detect neutrinos, elusive particles that travel through space with almost no interaction.
Last February, the KM3NeT scientific collaboration announced in Nature magazine the detection of the most energetic neutrino ever observed on Earth. As a key industrial partner, Exail plays a major role in the development of this extraordinary telescope, having already delivered over one million euros worth of high-tech equipment designed for operation in complex environments.
Installation of a detection unit of KM3NeT in the Mediterranean Sea, using Exail’s acoustic positioning solutions.
A deep-sea neutrino observatory
Neutrinos are tiny, electrically neutral particles that pass through the Earth with virtually no interaction with matter. Detecting them can help scientists better understand the astrophysical phenomena that generate them. But this requires huge, highly specialized telescopes, deployed in remote locations far from disturbances.
The KM3NeT telescope is deployed in two locations: off the coast of Toulon, France (“ORCA”, 40 km offshore, 2500 m deep) and off the coast of Sicily, Italy (“ARCA”, 80 km offshore, 3500 m deep). It tracks high-energy particles as they pass through the Earth, by using a network of 6210 optical modules suspended underwater. These act like ultra-sensitive cameras that detect the faint flashes of light produced when a neutrino interacts with water molecules near the detectors– a rare but telltale sign.
It is virtually impossible to detect the neutrino directly, but we can detect the light generated by its interaction with the particles in the water. Lined up along 700-meters-high vertical cables, these modules form a vast detection array. Once fully completed, KM3NeT will cover a volume of one cubic kilometer, making it the largest neutrino telescope in the world!
The KM3NeT telescope involves more than 350 researchers and engineers from 21 countries, along with industrial partners such as Exail. Although only 20% of the telescope is currently deployed, it has already made history by detecting the most energetic neutrino ever recorded – traced back to an as-yet-unknown cosmic event.
Schematic representation of the KM3NeT observatory (similar on both ORCA and ARCA parts), and its connection to the digital infrastructure on land
Exail's solutions for the KM3NeT project
As a key industrial partner, Exail has provided its expertise in underwater acoustic positioning and integrated micro-optical systems to support the deployment and operation of the KM3NeT telescope.
Integrated micro-optical systems: Exail provides integrated micro-optical assemblies that are essential for transmitting large volumes of scientific data from underwater sensors through optical fibers. Exail’s MUX/DEMUX (multiplexer/demultiplexer) integrated system enables different wavelengths carrying data from different sensors to be combined (at the entrance) and separated (at the exit) in a single optical fiber, enabling high-speed transmission over long distances. More than 100 MUX/DEMUX systems have been delivered since 2012, to equip KM3NeT’s digital infrastructure on land, but also offshore where they are integrated into the junction nodes (see below schematic representation).
« Our ultra-compact micro-optical systems, initially developed for telecommunications, have proven their reliability in extreme environments, here in deep-sea, but also in outer space » - Etienne Decerle, Sales director – Quantum & integrated photonics products at Exail
Exail's MUX micro-optical module integrated into the junction box, before deployment. A multiplexer enables different wavelengths to be combined into a single optical fiber.
Acoustic positioning ensures precise deployment of equipment in the deep sea, where no other positioning solution is relevant. Exail supplied advanced acoustic solutions to install the first KM3NeT sensors in 2017 (ORCA, France), at depths of over 2,000 meters with great precision. In July 2025, Exail supported a major sea campaign aiming at expanding KM3NeT (ARCA, Italy) with new detection units using a cutting-edge acoustic positioning system allowing a sub-meter precision at record deep-sea (nearly 3500 m).
« In 2017, a Ramses system and specially designed long-life titanium transponders were used to deploy optical module lines on the French part of the telescope (ORCA). A Hydrins inertial navigation system was also installed on the deployment vessel. In 2025, a Ramses system and four long-life Canopus beacons enabled the deployment of 18 new detection units for the Italian part (ARCA), at even greater depths. » - Pierre-Yves Morvan, product manager at Exail
Schematic representation of the deployment of KM3NeT optical modules (ARCA, Italy) using acoustic positioning. Several optical modules lines are connected to a junction box that features Exail’s MUX/DEMUX module.
"Exail has been a reliable industrial supplier to KM3NeT since the early stages, demonstrating the capability to meet our specific technical requirements for this highly challenging application. We rely on their support and expertise for the entire span of the project." Antonio D'Amico, KM3NeT Technical Project Manager
New acoustic triangulation system using long-life Exail’s Canopus beacons enabled sub-meter precision during the summer 2025 sea campaign, successfully deploying 18 new detection units at KM3NeT ARCA (Italy / INFN).