國際海洋資訊

Secrets Beneath the Sea:
The Internet Superhighways Connecting the World

The internet we use every day is just like a vast global network of superhighways. Terms like "cloud" or "satellite communications" are often mentioned, while in reality, nearly 99% of all cross-border internet data is transmitted through physical cables laid on the seafloor (Taiwan Submarine Cable and IDC Industrial Policy Website, 2024). Undersea cables, consequently, have become the invisible superhighways of our digital lives. They transmit data at incredibly high speeds, offer exceptional reliability, and carry far more information than satellites. A single submarine cable can be in service for over 25 years, enabling everything from our daily e-mails and video calls, to international financial transactions. Almost all these online activities rely entirely on these hidden network beneath the sea.

With the tremendous growth in demand for cloud computing, AI, big data, and streaming media, the need for submarine cables has skyrocketed. Not just traditional telecom operators, tech giants like Google, Meta, Microsoft, and Amazon are investing billions of dollars into submarine cables. They have become the key players in laying the next generation of submarine cables, ensuring seamless global information flow.

However, the diameter of most undersea cables is roughly comparable to that of a standard garden hose. In coastal shallow waters, even when they are buried under the seabed for protection, the submarine cables remain quite vulnerable and can be severed or damaged by fishing trawlers or ship anchors. Aside from accidents, geopolitical tensions have also cast a shadow over submarine cable security. These submarine cables, buried deep beneath the sea, could potentially become new targets for malicious attacks. Recent incidents of submarine cables being mysteriously severed in regions like the Red Sea and the Baltic Sea have heightened such concerns.

This article reviews recent literature to outline the major global submarine cable events since 2023, including new constructions and upgrades, international cooperation and policy adjustments, as well as technological innovations and future trends. It aims to allow readers to understand the critical role of submarine cables in modern telecommunications, as well as how Taiwan should respond to global trends in order to strengthen its own submarine cable resilience. 

▲Figure 1. Global Submarine Cable Distribution Map
Photo Credit: Submarine Cable Map

Major Submarine Cable Incidents Since 2023

Red Sea Submarine Cable Disruption

In early 2024, submarine cables disruption occurred to three major international in the Red Sea almost at the same time. These included the SEACOM/Tata TGN-Eurasia cable, which connects Africa's east coast to Egypt; the Europe India Gateway (EIG) cable, which links Europe, the Middle East, and India; and the Asia-Africa-Europe-1 (AAE-1) cable. The disruption caused severe internet congestion across East African countries such as Kenya and Somalia, as well as in many parts of South and Southeast Asia. Users experienced significant slowdowns and in some cases complete service outages (Wooden, 2024). Initial estimates indicated that around 25% of Eurasian data traffic was affected, while later analysis suggested the impact could have reached as much as 70% of actual data traffic. Many speculated that it was a deliberate act of sabotage by Houthi. However, experts soon pointed out that in order to precisely severe multiple durable submarine cables hundreds of meters below the surface, it would require highly specialized equipment and expertise, and hence it is unlikely to be the Houthi. As the investigation proceeded, the result seems to point at the cargo ships in the area. According to the International Cable Protection Committee (ICPC), one of the main possible causes of this disruption was a ship's anchor from an undermined cargo ship, which had fallen on the seabed (Madory, 2024).

This situation reveals the extended impact of wars and conflicts on global infrastructure. Even when global critical infrastructures carrying our digital life are not directed targeted, they can still be crippled by modern military confrontations. This incident serves as a stark reminder to the international community on the importance of safeguarding the stability of submarine cables, especially in an era of rising geopolitical risk.

Baltic Sea Submarine Cable Disruption

In addition to the volatility in the Red Sea, the seemingly calm Baltic Sea in Northern Europe has also seen a series of unusual cable and pipeline disruptions in recent years, raising serious security concerns among neighboring countries. In October 2023, a submarine natural gas pipeline connecting Finland and Estonia, and an adjacent telecommunications cable to that natural gas pipeline, were found damaged at almost the same time(Graphic News, 2023, October 18). Investigators later discovered drag marks on the seabed near the site (likely caused by a heavy object such as an anchor) and identified suspicious vessels that had transited the area during the incident.

Statistics show that in the short span of just 15 months starting in the second half of 2023, the Baltic region experienced at least 11 cases of damage to submarine cables or pipelines. The most recent case occurred in January 2025, when a submarine cable connecting Latvia to Sweden was found severed (Central News Agency, 2025, January 27). In response, NATO launched a monitoring operation targeting the Baltic Sea.

This series of incidents in the Baltic area underscores a sobering reality. Amid the heightened geopolitical tensions today, the long-overlooked submarine cables issue have become a new front-line role in national security and a potential flashpoint in future conflicts.

New Construction and Upgrades of Submarine Cables

In response to the growing cases of submarine cable disruptions, countries around the world are accelerating their efforts, investing heavily in building the next generation of more resilient submarine cable infrastructure. Several ongoing projects are noteworthy, including:

SEA-ME-WE 6 Submarine Cable

Amid the global trend of strengthening network resilience, a new generation of ultra-high-speed submarine cable systems is under construction. One of the most prominent is the Southeast Asia–Middle East–Western Europe 6 (SEA-ME-WE 6, or SMW6) cable, which is set to become the backbone of next generation ultra-high-speed telecommunication. The SMW6 system starts in Singapore, passes through South Asia and the Middle East, and terminates in France. It stretches approximately 21,700 kilometers, including over 20 landing points across 17 to 18 countries, such as Bangladesh, Saudi Arabia, Turkey, and Italy, making it a truly intercontinental data superhighway (Submarine Networks, n.d.-a).

SMW6 employs Space Division Multiplexing (SDM) technology and boasts a design capacity of up to 126 Tbps—a multiple of its predecessor SMW5, which offered around 24 Tbps. This capacity is fast enough to support millions of users streaming ultra-high-definition video simultaneously.

Beyond its technological significance, the construction of SMW6 also reflects the shifting geopolitical dynamics. Some Chinese companies had expressed interest in bidding on the project. However, the US had cybersecurity concerns and that ultimately led to SubCom, a US-based company, winning the contract. The system is expected to become operational between late 2025 and early 2026, helping to alleviate traffic bottlenecks in the Red Sea and Egypt, to enhance the stability of the Asia–Europe internet corridor, and to serve as a pillar to the telecommunications of these three continents.

Deep Blue One Submarine Cable

In the Atlantic region, the Deep Blue One submarine cable system, led by the Digicel Group, is bringing new connectivity momentum into the Caribbean and northern South America. This cable spans approximately 2,250 kilometers, linking French Guiana, Guyana, Suriname, and Trinidad and Tobago. It includes five landing points and features 2 to 8 fiber pairs, each capable of supporting 12 Tbps, with a total design capacity of 25 Tbps. The system significantly boosts the region's digital connectivity and network service quality, and was ready for service since May 2024(Submarine Networks, n.d.-b). The construction of this submarine cable carries not only regional geopolitical significance but also responds to the recent development in the region. That includes the discovery of offshore oil fields in Guyana and Suriname's rapid rise in the energy sector, both of which have driven demand for high-speed telecommunications. Deep Blue One was specifically designed with an extendable branching structure to meet the connectivity needs of offshore oil drilling platforms, which would be of great help to supporting the growing energy industry in the region.

From a technical perspective, Deep Blue One offers high capacity and low latency, enabling direct connectivity between Europe and the Americas via network nodes in France and the United States. Economically, the submarine cable plays a vital role in supporting digital transformation and attracting foreign investment in Guyana and Suriname. It fills a long-standing gap in telecommunication infrastructure of the region, benefiting millions of residents there while also enhancing the network resilience and economic integration of the Caribbean region.

▲Figure 4. Asia Africa Europe-1, AAE-1 / Photo Credit: Submarine Cable Map

A Global Call to Action: Building a Submarine Cable Safety Net

In the face of growing threats from natural disasters, accidental damage by fishing vessels, and even potentially intentional acts of sabotage, governments and international organizations around the world are taking proactive steps to establish a stronger safety net for submarine cables. In November 2024, the U.S. Federal Communications Commission (FCC) announced the launch of the first comprehensive review of its submarine cable regulatory framework since 2001 (Federal  Communications Commission, 2024, November 21). This initiative underscores the United States' commitment to strengthening cybersecurity as part of its national security. The FCC introduced several new regulatory measures, including banning foreign companies who were previously denied licenses on national security grounds from participating in U.S. submarine cable projects, and prohibiting the use of equipment from "untrusted" suppliers. This has highlighted the US's heightened focus on supply chain security. Protecting submarine cables cannot rely solely on the efforts of any single nation. United Nation specialized agencies, such as the International Telecommunication Union (ITU) and the International Cable Protection Committee (ICPC), have recognized the global nature of this challenge. In November 2024, these two organizations jointly established the International Advisory Body for Submarine Cable Resilience, bringing together around 40 experts from governments, industries, NGOs, and academia. This cross-border, cross-sector platform aims to facilitate the global exchange and coordination of technology as well as the best practices in submarine cable operations and management. The goal is to ensure operational resilience in the face of disasters or emergencies, so that no place in the world becomes an information silo when a single submarine cable goes down (International Telecommunication Union, n.d.).

The establishment of this new body sends a clear message: submarine cables are no longer just silent data carriers. It is now at a level of strategic importance where it can impact national security and global stability. By incorporating submarine cables into multilateral security cooperation mechanisms, international organizations are signaling their determination to collectively mitigate systemic risks that no single country can shoulder alone.

Faster and Higher-Capacity Submarine Cable Technology

Expanding the "Lanes" ― Space Division Multiplexing (SDM)

The central idea behind SDM (Space Division Multiplexing) is by laying more fiber pairs within a single submarine cable to greatly increase the total transmission capacity. The next-generation submarine cables using SDM technology can pack 12, 16, or even over 24 fiber pairs into a single cable (Tinka, 2023, May 2)! Within the next five years, super cables capable of transmitting data at Pbps (Petabits per second, equal to 1,000 Tbps or a million Gbps) will no longer be just a dream.

The Ultimate "Cloning" Technology: Multi-core Fiber (MCF)

MCF (Multi-core Fiber) technology integrates multiple independent optical channels (cores) into a single fiber. Japan has already successfully completed long-distance submarine cable transmission tests using 4-core and even 19-core optical fibers. Google is also planning to adopt dual-core fiber for the first time in its new submarine cable project co-developed with Chunghwa Telecom.

The Ultimate "Cloning" Technology: Multi-core Fiber (MCF)

More Resilient: With advanced technology and increased security awareness, future undersea cable construction will become more resilient. Countries are trying to reduce dependence on single vulnerable routes by planning new cable corridors. For example, new shortcuts across the Arctic connecting Europe and Asia have been proposed (Norway is already building the world's northernmost submarine cable), and Meta has proposed "Project Waterworth," an ultra-long cable plan encircling five continents. The goal is to establish more backup routes to enhance the overall resilience of the internet (Moss, 2025).

More Intelligent: More Intelligent: The new generation of submarine cables will be equipped with more sensors capable of reporting their health status in real-time (such as temperature and optical power), some of them may further utilize acoustic sensors to detect dangerous vibrations from nearby ships dragging anchors. Combined with AI analysis, potential problems can be identified earlier, high-risk areas predicted, and maintenance schedules optimized. In the future, underwater robots may conduct regular patrols to prevent problems before they occur.

More Collaborative: Whether jointly investing in new routes or sharing maintenance vessel resources, cross-national coordination is essential. Recent incidents have actually alerted and increased countries' willingness to cooperate in enhancing resilience. For instance, European countries established an underwater infrastructure working group after the Baltic Sea incidents, while Asia-Pacific regions are discussing the creation of a regional cable damage notification mechanism. As the global economy grows increasingly dependent on digital infrastructure, disruption to any critical submarine cable is no longer just one country's problem but an event affecting global supply chains and communication flows.

Safeguarding Submarine Cables to Secure Our Digital Future

Submarine cables are the lifelines of the modern internet-driven world. As demonstrated by a series of incidents since 2023, whether accidental disruptions caused by conflict or potential deliberate sabotage, these events have sounded a global alarm for both telecommunications and the economy. In the meantime, the surge in next-generation cable technologies and infrastructure projects offers a sense of hope. A faster and more resilient foundation for Internet network is taking shape, and the international community is taking actions to echo such changes. From strengthening regulations and setting boundaries to experts jointly forming new advisory institutions and dialogue on strategies, countries around the world are putting in efforts to establish firm and strong protection for this infrastructure undersea. Though buried deep beneath the oceans, submarine cables require our collective attention and commitment to ensure their security and continued development. Through global cooperation, we can fasten these invisible lines with the future of the connectivity for the human society.

▲Figure 5. Key information of Submarine Cables / Photo Credit: The Editorial Team / Data Reference: Submarine Cable Map

References

1. Central News Agency. (2025, January 27). Submarine cable between Sweden and Latvia damaged, raising concerns about Russian hybrid warfare. Central News Agency . https://www.cna.com.tw/news/aopl/202501270005.aspx
2. Federal Communications Commission. (2024, November 21). FCC Launches First Major Review of Submarine Cable Rules in Decades. Federal Communications Commission. https://www.fcc.gov/document/fcc-launches-first-major-review-submarine-cable-rulesdecades
3. Graphic News. (2023, October 18). Conflict in Baltic Sea cable damage. Graphic News. https://www.graphicnews.com/en/pages/44971/conflict-baltic-sea-cable-damage
4. International Telecommunication Union. (n.d.). International Advisory Body for Submarine Cable Resilience. International
5. Telecommunication Union . https://www.itu.int/digital-resilience/submarine-cables/advisory-body/
6. Wooden, A. (2024, October 8). Red Sea cable cuts' impact was 'severely underestimated'. Telecoms . https://www.telecoms.com/telecoms-infrastructure/red-sea-cable-cuts-impact-was-severely-underestimated-
7. Madory, D. (2024). What caused the Red Sea submarine cable cuts? Kentik . https://www.kentik.com/blog/what-caused-the-red-seasubmarine-cable-cuts/
8. Moss, S. (2025). Project Waterworth: Meta announces world's longest subsea cable project spanning five continents. Data Center
9. Dynamics . https://www.datacenterdynamics.com/en/news/project-waterworth-meta-announces-worlds-longest-subsea-cableproject-spanning-five-continents/
10. Submarine Networks. (n.d.-a). SEA-ME-WE 6. https://www.submarinenetworks.com/en/systems/asia-europe-africa/smw6
11. Submarine Networks. (n.d.-b). Deep Blue One. https://www.submarinenetworks.com/en/systems/brazil-us/deep-blue-one
12. Tinka, M. (2023, May 2). Spatial Division Multiplexing ― a new (subsea) cable paradigm. APNIC Blog. https://blog.apnic.net/2023/05/02/spatial-division-multiplexing-a-new-subsea-cable-paradigm/.

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