Submarine Cables: the backbone of the Internet

Submarine cables are the unsung heroes of the modern Internet. Stretching across the oceans, these fibre optic networks quietly enable the seamless exchange of massive amounts of data, powering everything from video calls to cloud services.

Though rarely acknowledged, they are the foundation of the global connectivity we rely on daily. Without them, the interconnected world as we know it wouldn’t function.

The essential role of Submarine Cables in Global Connectivity

Submarine cables carry about 99% of the world’s data, connecting continents and enabling communication between countries, businesses, and individuals. These systems form a global capillary network that spans oceans, linking key data centres and Internet hubs.

Despite their importance, submarine cables remain invisible to most users, hidden beneath thousands of meters of water. Yet, they are essential for the modern digital economy, supporting e-commerce, online education, telemedicine, and countless other applications.

The origins and evolution of Submarine Cables

Submarine cables have a long history dating back to the mid-19th century when the first telegraph cables were laid across the Atlantic. Over time, technological advancements transformed these cables from supporting simple text messages to handling terabytes of data per second.

The current generation of fibre optic submarine cable systems relies on advanced materials and cutting-edge technology to deliver exceptional performance and ensure reliability even in harsh underwater environments.

Submarine Cables vs. Satellites & why cables are superior

As demonstrated in Figure 1, the capacity of one fibre pair of the MAREA cable (RFS in 2018) is higher than the total bandwidth of the SpaceX (Starlink) constellation in 2019¹.

While satellites are often thought to dominate the Internet infrastructure, this must be clarified. Submarine cables far exceed satellites in key performance metrics:

Bandwidth Capacity

Submarine cables provide unparalleled bandwidth, measured in terabits per second (TB/s). In contrast, satellite bandwidth is measured in gigabits per second (GB/s). For example, the EllaLink cable delivers 25 TB/s per fibre pair between Europe and Latin America.

Latency

Latency, or the delay in data transmission, is significantly lower for submarine cables. Satellites, positioned thousands of kilometres above Earth, have higher latency due to the physical distance data must travel. Submarine cables are far more reliable for latency-sensitive applications like financial trading, gaming, and video conferencing.

Stability

Submarine cables benefit from the relatively stable underwater environment. Satellites are subject to space weather conditions, such as solar storms, which can disrupt communications.

Real-World examples of Submarine Cable performance

The EllaLink cable, launched in 2021, highlights the superior performance of submarine cables:

• Bandwidth: 25 TB/s capacity between servers in Sines, Portugal, and Fortaleza, Brazil.
• Latency: less than 60 milliseconds, enabling near-instantaneous data transfer.
• Efficiency: a single fibre pair on the EllaLink cable can handle more data than entire satellite constellations.

Additionally, cables like the MAREA cable set benchmarks for connectivity, demonstrating the immense potential of these systems to transform global communication.

The challenges of Submarine Cable deployment

The deployment of submarine cables is a complex and costly process involving several stages:

• Route Planning – Engineers carefully map routes to avoid underwater hazards, such as deep-sea trenches and active volcanoes.
• Cable Manufacturing – Cables are made to withstand immense pressure and temperature variations under the sea.
• Installation – Specialized ships lay cables on the ocean floor, which can take months or even years for long routes.
• Maintenance – Submarine cables are regularly inspected and repaired when damaged by fishing activities, ship anchors, or natural events.

Despite these challenges, the benefits of submarine cables far outweigh the costs, making them a crucial investment for global connectivity.

Satellites: complementing Submarine Cables

While submarine cables dominate the global Internet backbone, satellites still play a vital role in specific use cases:

• Remote Areas – Satellites provide connectivity in isolated regions where laying cables is impractical, such as deserts, mountain ranges, or sparsely populated islands.

• Disaster Recovery – Satellites can offer emergency communication services when natural disasters disrupt terrestrial networks. This symbiotic relationship ensures that both technologies contribute to a connected world, though submarine cables remain the primary infrastructure for international data exchange.

Why Submarine Cables are the Internet backbone

Submarine cables enable several critical Internet functions:

• Global Data Exchange – 99% of international data is transmitted via submarine cables.
• Cloud Computing – Cloud services depend on high-speed, low-latency connections provided by submarine systems.
• E-commerce – Businesses rely on fast and reliable communication for online transactions.
• Scientific Collaboration – Research institutions use submarine cables to share massive datasets for climate modelling or space exploration projects.

As Internet demand continues to grow, the submarine cable network must expand to meet future requirements:

• Increased Capacity – Emerging technologies like 5G and edge computing will require even greater bandwidth.
• Geographic Expansion – New routes are being developed to connect underserved regions, such as parts of Africa and the Pacific Islands.
• Enhanced Resilience – Redundancy and innovative materials will help submarine cables withstand environmental and man-made threats.

Submarine cables will remain the Internet’s cornerstone, evolving alongside technological advancements.

Submarine cables are the unsung heroes of the Internet age, providing the infrastructure that makes global communication possible. While satellites are valuable complements, submarine cables excel in bandwidth, latency, and stability, solidifying their role as the Internet’s backbone.

Every aspect of modern life depends on these underwater marvels, from streaming your favourite shows to running cloud-based applications. As demand for connectivity grows, investing in and expanding submarine cable networks will ensure a connected and prosperous future.