AP Sensing and Sumitomo Electric have demonstrated a new approach to continuous monitoring of long-distance HVDC submarine cables. By combining Distributed Acoustic Sensing (DAS) with advanced optical transmission technology, the solution can monitor cable systems spanning more than 600 km.
The joint development received the Best Paper Award for Future Cable Systems and Innovative Cable Applications (Category B1 PS1) at the CIGRE Paris Session 2026.
Extending DAS Monitoring Beyond 300 km
Renewable energy generation is expanding, often far from major demand centers. This means more power needs to be transmitted over long distances, driving the need for longer, higher-capacity HVDC submarine cable connections.
Damage caused by anchors, fishing equipment and other external activity can result in costly outages, while locating an incident across such long subsea routes can be challenging.
The new approach combines AP Sensing’s DAS technology with Sumitomo Electric’s ultra-low-loss Z-PLUS FiberTM 130ULL optical fiber and remotely pumped erbium-doped fiber amplifier (EDFA) technology.
This enables acoustic monitoring over more than 300 km from one end of the cable. By monitoring from both ends, a submarine cable system exceeding 600 km can be covered continuously and in real time.
Improving Location Accuracy by More Than 30 times
Conventional fault-location methods have an accuracy of approximately 1% of the cable length. For a 600 km submarine cable, this can mean an uncertainty of around 6 km, leaving a substantial area of seabed to inspect following an incident.
With the new monitoring approach, the theoretical location uncertainty across a 600 km cable monitored from both ends is reduced to less than 200 meters.
A field demonstration off Awaji Island, Japan, put this accuracy to the test. Using an optical fiber integrated into an HVDC submarine cable, a weight was dropped near the 262 km point to simulate a ship anchor impact. AP Sensing’s DAS system detected the event in real time and located the simulated impact within approximately 68 meters of its actual position.
More precise localization can reduce the area requiring offshore inspection and help operators respond faster when incidents occur. DAS can also detect acoustic signatures associated with external activity around a cable, providing additional visibility into potential threats to critical submarine infrastructure.
Recognized at CIGRE Paris Session 2026
These findings were presented in the paper “Early Detection of External Damage Incidents in Long-Distance Direct Current Submarine Cables” (Paper ID 10824). Authors Seiji Yamamoto, Soichiro Takeda and Takefumi Shimoguchi of Sumitomo Electric, together with Denis Bolotov and Ralf Albrecht of AP Sensing, received the CIGRE Best Paper Award in the Future Cable Systems and Innovative Cable Applications session (B1 PS1), part of Study Committee B1 on Insulated Cables. The achievement by Sumitomo Electric Industries, Ltd. is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
