Undersea Cables: The Invisible Highways of Global Internet

Red buoy markers mark the path of a submarine cable being laid in the ocean. The Second International Submarine Cable Resilience Summit will take place on 2–3 February 2026 in Porto, Portugal.

Every day, we send countless emails, take part in video calls, use search engines and streaming services, and bank online seamlessly.

The exchange of data in the blink of an eye has become a given in much of the world — yet we rarely pause to think about what makes it all possible: a complex global network of cables lying deep in the ocean that silently connects us.

In the modern information age, undersea cables have become the backbone of digital connectivity, Tomas Lamanauskas, Deputy Secretary-General of the International Telecommunication Union (ITU), told UN News ahead of a global summit on the issue beginning in Portugal on Monday.

Trillions of dollars in global economic transactions and the continuous flow of information take place through this network.

“About 99 per cent of international internet traffic goes through submarine cables. Even the conversation you and I are having right now is carried through these cables,” he said.

“People know the visible access points, such as mobile networks, satellites and fixed internet, but the underlying infrastructure that supports them is the vast network of submarine cables — our digital highways.”

These invisible highways, consisting of fibre-optic wires connecting landing points, are laid hundreds of metres below the ocean’s surface by cable-laying ships.

Mr Lamanauskas underscored that as reliance on digital connectivity continues to grow, strengthening the resilience of these cables and developing collective strategies have become increasingly important.

This will be a key focus of the Second International Submarine Cable Resilience Summit, taking place on Monday and Tuesday in Porto, Portugal.

Rapid data transmission

Connecting different parts of the world through communication cables is not a new idea. In 1850, England and France were linked for the first time by an undersea telegraph cable.

Since then, technology has steadily evolved — from telegraph services to telephone networks, and now to high-speed internet carried by fibre-optic cables. Today, hundreds of terabits of data pass per second through cables laid along the seabed.

Across the globe, there are more than 500 commercial submarine cables linking continents, markets and households.

Relatively thin and roughly the width of a garden hose, these cables stretch for about 1.7 million kilometres — long enough to wrap around the Earth several times.

Before installation, the seabed is surveyed to identify routes with fewer risks and minimal environmental impact. Special ships then unroll large reels of fibre-optic cable onto the ocean floor.

Cable traffic disrupted

As these cables increasingly form the backbone of the global economy, any disruption in data flow can be instantly felt, affecting economic activity, emergency and technology services, security systems, and internet access for billions worldwide.

Typically, there are between 150 and 200 cable incidents each year, averaging three to four per week.

The ITU official recalled that “in recent years, there have been several high-profile incidents, from the Red Sea to West and East Africa.

“For example, in 2024, submarine cable incidents in the Red Sea disrupted an estimated 25 per cent of data traffic between Europe and Asia.”

Outages may result from earthquakes, underwater landslides and volcanic eruptions. However, statistics show that around 80 per cent of incidents are caused by human activity, such as ship anchors or fishing trawlers damaging cables.

Every millisecond matters

Mr Lamanauskas cited Tonga, which has experienced three major disruptions since 2019 due to earthquakes, volcanic eruptions and improper anchoring. In remote regions lacking network diversity, a single cable cut can take vast areas offline.

“Imagine your entire community being offline for a week, unable to access essential services such as digital healthcare, information and education,” he said.

“Now imagine the impact on stock traders in New York if even a millisecond delay occurs due to cable congestion or an incident. Every moment matters.”

Repairing the invisible highways

Aside from natural wear and tear, “a portion of the cable infrastructure laid around the dot-com boom of 2000 is now reaching maturity, as these cables were designed for an average lifespan of 25 years,” he added.

Mr Lamanauskas explained that while engineers can usually identify damaged sections quickly, “the actual repair work is not always the most complicated part. What is often more complex is securing the necessary permits and licences, particularly when multiple jurisdictions are involved.”

Depending on the location and scale of damage, repairs may take days, weeks or even months. While cable ships are often nearby in busy regions, reaching remote areas can take significantly longer. In many countries, the absence of a clear coordinating authority further complicates the process.

Laying new cables, he noted, is often a multi-year and costly endeavour. “There is extensive planning involved. Shorter cables cost millions of dollars, while longer ones can run into the hundreds of millions.”

What is ITU doing?

As the UN agency for digital technologies, ITU works to strengthen the resilience of global submarine cables through collaboration, standard-setting and technical guidance. Its priorities include improving resilience measures, streamlining maintenance and repair processes, and promoting more sustainable practices.

“Over the past 40 years, the capacity of optical cables has been increasing by about 40 per cent annually. This exponential growth has powered the expansion of the internet,” Mr Lamanauskas said.

He clarified that ITU is not an operational body and does not repair cables.

“Instead, we focus on creating the right enabling environment — shortening permitting timelines, establishing clear points of contact, raising awareness to prevent accidental damage, and facilitating faster repairs.”

As demand for connectivity and data continues to surge at unprecedented speed, these efforts will play a vital role in strengthening the foundations of global digital connectivity and shared progress.