The fragility of subsea cables

In the latest episode of For Tech’s Sake, we dive deep under the sea to explore the world of internet cables, from the Victorian internet to modern-day fibre.

There’s so much language used about the online world that it suggests it has no physical form – that it’s just in the air or rather the cloud, wirelessly transmitting from one device to the next.

But the truth is these wireless devices and cloud computing actually rely on huge numbers of physical cables that run across the world via the seabed.

These long cables lie on the ocean floor and send data as pulses of light inside thin strands of wires, or optical fibres, within the cable. Roughly 99pc of the world’s internet traffic runs through these cables.

Ireland has a very long history with subsea cables, starting with the world’s first transatlantic cable, which sent its first telegram 166 years ago from Kerry’s Valentia Island to Heart’s Content in Newfoundland.

Currently, Ireland has 14 cables, four of which connect to the US and one of which connects to Iceland, while the rest connect to the UK. There are many more cables spreading across the rest of the world.

Subsea cable map. Image: TeleGeography (CC BY-SA 4.0)

But while these cables are amazing engineering and technical feats, keeping us connected online, the physical nature of them also means they are susceptible to damage, which could risk cutting us off.

In the latest episode of For Tech’s Sake, Deryck Fay, author of Connecting A Nation: The Story of Telecommunications in Ireland, takes listeners through a potted history of the development of these cables before examining the modern-day challenges.

“Maybe we fret too much about terrorist attacks or something like that. In fact, most of the damage comes from the near shore, such as fishing nets,” said Fay.

“If you’re a smaller, poorer island and you have only got one or two [cables], you can literally lose the internet, because a fishing trawler snags the only cable connecting to the rest of the world and there’s quite a few examples [in the] Pacific over the last few years.”

In fact, just this year, there have been widespread, lengthy internet outages across portions West and Central Africa, parts of East Africa and South Asia, and Tonga all because of damage to submarine cables. In fact, this is the third time in recent years that Tonga has faced this problem. In 2019, a cable was severed by a ship’s anchor, while in 2022 the island nation was once again cut off following an underwater volcanic eruption.

Fay will feature in an upcoming RTÉ One documentary, The Cable That Changed the World, on 12 August 2024.

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