Finland tests acoustic monitoring for CUI protection

An ROV being used by the Finnish Border Guard to test acoustic monitoring for undersea cable protection, in a trial announced on 5 June 2026. (Finnish Border Guard)

The Finnish Border Guard (FBG) is heading a project to create better early warning of threats to critical undersea infrastructure (CUI), the FBG announced on 5 June 2026.

The FBG said it had tested new detection equipment in the Baltic Sea using a remotely operated vehicle (ROV) launched from the FBG vessel Uisko in conjunction with the Finnish navy project partner companies.

The equipment used distributed acoustic observation to identify a potential risk to CUI. The tests sought to asses whether this anticipatory identification could prevent or reduce large-scale damage.

Distruibuted Acoustic Sensing (DAS) uses fibre optic cables to detect and measure atypical vibrations on the seabed. DAS analyses changes in the reflections of light from the fibre optics which could then be used to detect the approach of a ship dragging its anchor.

“The FBG is leading the work on the EU Cable Communication [EUCC] Notice, and by enabling these tests, we promote new ways of protecting and detecting EU Baltic Sea littoral states' infrastructure. It is important that in addition to the authorities, companies that own the infrastructure are involved too,” said Ilja Iljin, an expert preparing implementation of the EUCC at FBG headquarters.

Other partners in the project include Finland's Naval War College, the Fingrid and Gasgrid energy transmission companies, the Geological Survey of Finland, the University of Helsinki's Institute of Seismology, and Elisa, a major telecommunications company. Elisa's Finland–Estonia telecommunications cable was among those damaged by the Eagle S, which dragged its anchor across the seabed on Christmas Day 2024.