BCS East-West Interlink

Overview

The BCS East-West Interlink is a submarine communications cable spanning approximately 218 km across the Baltic Sea. Commissioned in 1997, the cable was owned and operated by Arelion. It connected Šventoji, a coastal town in Lithuania, with Katthammarsvik, located on the eastern shore of Gotland, Sweden. Designed to provide a direct communication link between the two countries, it served as part of the broader Baltic Sea subsea infrastructure. While not a high-capacity or technologically advanced cable by modern standards, its strategic placement made it a significant asset for regional connectivity.

The cable remained operational for 27 years until it was damaged on 18 November 2024, an event that coincided with the disruption of another Baltic cable, C-Lion1, in a separate corridor. This incident highlighted the vulnerabilities of subsea infrastructure in the Baltic region, where dense shipping activity, geopolitical tensions, and aging systems intersect. The BCS East-West Interlink's role in this broader context underscores the importance of monitoring and maintaining undersea cables, even those considered less prominent.

Route and Landings

The BCS East-West Interlink traversed the Baltic Sea, connecting the Lithuanian coast at Šventoji with the Swedish island of Gotland at Katthammarsvik. The route was relatively direct, crossing open waters at depths ranging from 100 to 150 meters. The Baltic Sea is characterized by its shallow depth compared to other major bodies of water, which simplifies cable laying but also increases the risk of damage from anchors, fishing activities, and other maritime operations.

Šventoji, located near the northern edge of Lithuania's coastline, serves as a gateway to the Baltic and is a logical choice for cable landings due to its proximity to regional hubs. Katthammarsvik, on Gotland, is strategically positioned in the central Baltic Sea, making it a critical point for both Swedish and regional connectivity. Gotland's geographic importance has long been recognized, as it provides a central vantage point for monitoring and securing Baltic Sea activities. The cable's route not only facilitated communication between Lithuania and Sweden but also contributed to the resilience of the Baltic region's overall telecommunications network.

Ownership and History

The BCS East-West Interlink was owned by Arelion, a major operator in the global telecommunications market. It became operational in 1997, during a period of rapid expansion in submarine cable infrastructure across Europe. Its deployment reflected the growing need for reliable cross-border communication links in the Baltic region, particularly as Lithuania and other Baltic states integrated more closely with Western Europe following the end of the Cold War.

On 18 November 2024, the cable was damaged in an incident that also affected the C-Lion1 cable between Finland and Germany. The simultaneous disruptions raised concerns about the security and resilience of Baltic subsea infrastructure. The BCS East-West Interlink was subsequently taken out of service, marking the end of its operational life. This event became part of a broader pattern of incidents in the Baltic Sea during 2023-2024, which included damage to other submarine cables and energy infrastructure.

What Our Measurements Show

Our live monitoring of the BCS East-West Interlink included 178 measured corridors, with a best round-trip time (RTT) of 17 milliseconds and an average RTT of 21 milliseconds. These metrics indicate that the cable provided relatively low-latency communication between Lithuania and Sweden, consistent with its relatively short length and direct route.

The nearly simultaneous damage to the BCS East-West Interlink and C-Lion1 underscores the interconnected risks faced by submarine cables in the Baltic region. The Baltic Sea's narrow corridors and dense maritime traffic create a challenging environment for subsea infrastructure. Our probes have highlighted the importance of monitoring vessel activity, anchor dragging, and other potential threats to cable integrity. The incident also revealed the need for improved redundancy and route separation to enhance the resilience of regional networks against correlated risks.

In conclusion, while the BCS East-West Interlink was not a high-profile cable, its role in the Baltic connectivity ecosystem and its involvement in the 2024 incident demonstrate the critical importance of even older, less prominent systems in maintaining global communications infrastructure.