Undersea Fiber Cables

10 Nov Undersea Fiber Cables

Beneath the Waves: How Undersea Fiber Optic Cables Keep the World Connected

In today’s hyper-connected digital world, it’s easy to imagine the internet as a cloud of invisible signals transmitted wirelessly through the air. Yet, the reality is far more remarkable — the majority of our global data flows through thousands of miles of undersea fiber optic cables, silently lying on the ocean floor. These cables are the true backbone of the global internet, carrying over 95% of international data traffic and enabling everything from streaming Netflix and Zoom calls to global banking and cloud computing.

In this article, we dive beneath the waves to explore how these submarine fiber optic networks work, why they are essential, and the engineering marvels that keep the world online.

A Hidden Network Beneath the Ocean

Today, there are more than 500 active submarine cables crisscrossing the world’s oceans, stretching over 1.4 million kilometers — enough to wrap around the Earth more than 30 times. They connect major cities and data hubs such as New York and London, Lagos and Lisbon, Singapore and Los Angeles.

At the heart of these cables are bundles of optical fibers — strands of glass thinner than a human hair. These fibers transmit information as pulses of light, traveling incredible distances under the sea to connect continents and nations in real time. From social media platforms to financial systems, these undersea cables power the digital economy and ensure global connectivity.

From Copper Telegraphs to Fiber Optics: A Brief History

The story of undersea communications began in the 19th century, not with light but with electricity. In 1858, the first transatlantic telegraph cable connected Ireland and Newfoundland. Made of copper and insulated with gutta-percha, it transmitted just a few words per minute — and frequently failed under the ocean’s immense pressure.

Copper technology slowly improved over the decades, enabling telephone calls and later coaxial cables that could carry hundreds of voice channels. Yet the real revolution came in the 1980s with fiber optic technology. Fiber could transmit thousands of times more data than copper with minimal loss, making it ideal for long-distance undersea communication.

The first transatlantic fiber optic cable, TAT-8, was laid in 1988, linking the U.S., U.K., and France. With a capacity of just 280 megabits per second, it was a groundbreaking leap, laying the foundation for the high-speed internet we rely on today.

How Submarine Fiber Optic Cables Work

Modern submarine fiber optic cables are engineering marvels. Each cable contains only a few fiber pairs — typically between 4 and 12 — yet each pair can carry tens of terabits per second, enough for millions of simultaneous high-definition video streams.

The secret behind this capacity is Dense Wavelength Division Multiplexing (DWDM). Instead of sending a single signal, DWDM allows dozens or hundreds of wavelengths (colors of light) to travel simultaneously through each fiber, each carrying its own data stream. This effectively multiplies the cable’s capacity, turning a single fiber into a data superhighway.

However, even light signals degrade over long distances. To maintain data integrity, optical amplifiers — typically Erbium-Doped Fiber Amplifiers (EDFAs) — boost the signals without converting them back to electricity. These amplifiers are powered by a direct current that runs through the cable itself, fed from landing stations on either end. The combination of DWDM, optical amplification, and precision engineering makes undersea cables capable of transmitting massive amounts of data across thousands of kilometers.

Pioneering Systems: 2Africa, SEA-ME-WE 6, and Beyond

Some submarine fiber optic systems are nothing short of extraordinary.

SEA-ME-WE 6 (Southeast Asia–Middle East–Western Europe 6) spans over 19,000 kilometers, linking 14 countries.

2Africa, deployed by Meta (Facebook) and partners, will circle the African continent with more than 45,000 kilometers of cable, one of the largest undersea projects ever undertaken.

Pacific Light Cable Network, connecting the U.S. and Asia, runs 13,000 kilometers beneath the Pacific Ocean.

The Marea cable, built by Microsoft and Meta, connects the U.S. to Spain and has a capacity of 200 terabits per second — enough for 10 million HD video streams simultaneously.

Recent experiments in multicore fiber have also shown promise. NEC and NTT successfully transmitted optical signals across 7,280 km using a 12-core fiber, marking a milestone for long-distance, high-capacity undersea networks.

Challenges of Laying and Maintaining Submarine Cables

Installing a submarine cable is an extraordinary feat, but maintaining it presents its own challenges. Cables can be damaged by earthquakes, fishing equipment, or anchors, requiring specialized ships to retrieve and repair them. Repairs can take days or weeks and cost millions of dollars.

Despite these challenges, the reliability of undersea cables is remarkable, with availability often exceeding 99.99%. International cooperation, careful route planning, and precision engineering are crucial to maintaining this global network.

The Future of Undersea Fiber Optic Networks

The world’s appetite for data is insatiable. Streaming, cloud computing, AI, and international business all depend on these hidden digital arteries. Tech giants like Google, Meta, Microsoft, and Amazon are investing billions in private submarine cable projects to support their cloud infrastructure and global operations.

Emerging technologies, including space-division multiplexing (SDM), allow more fibers per cable, while advanced monitoring systems detect faults faster than ever. Meanwhile, multicore and few-mode fibers promise higher capacity, further enabling terabit-per-second networks. The ocean floor is increasingly becoming a critical battleground for digital infrastructure.

Why Submarine Fiber Optic Cables Matter

Without undersea fiber optic cables, the global internet would grind to a halt. They carry the lifeblood of international communication, connecting data centers, governments, businesses, and individuals. From everyday tasks like streaming a movie to high-stakes financial transactions, these invisible cables keep the digital world moving.

Next time you send an email, join a Zoom call, or stream a video from another continent, remember that your data is traveling thousands of meters below the ocean surface, racing along strands of glass through one of humanity’s most impressive engineering achievements.

Conclusion

Undersea fiber optic cables are the unsung heroes of the internet age. They are critical to global connectivity, enabling communication, commerce, and innovation across continents. From DWDM and optical amplifiers to multicore fiber technology, these cables represent decades of technological advancement, international cooperation, and engineering excellence.

As data demands continue to soar, submarine cables will remain essential, powering the next generation of high-speed, low-latency global networks. They are not just cables on the ocean floor; they are the veins of the digital planet, silently keeping the world connected.

To learn more about optical networking, explore our optical network training page.