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Digital lifelines: why subsea cabling keeps global connectivity afloat

When picturing the Internet, it’s easy to think of mobile masts, orbiting satellites and big city data centres – but much of the infrastructure supporting our digital world actually lies at the bottom of the ocean.

Providing vital connectivity between the world’s 778 Internet Exchange Points, subsea cabling remains the backbone of modern communications. In fact, 99% of international data travels across the 300 submarine cables currently crisscrossing the globe.

Under pressure

Subsea cabling has been supporting global communications for far longer than you might expect. The first submarine cable, designed for transatlantic telegraphs, was completed in 1858 and connected Ireland with Newfoundland (it lasted just three weeks before seawater intrusion and corrosion caused it to fail). While this early copper cabling was replaced by fibre optics during the 1980s, many of the challenges faced by 19th Century engineers are still around today.

With individual lines stretching as far as 24,000 miles, and running as deep as 25,000 feet, specialised ships are needed to unspool cabling across the seabed. Even today, cable-laying is an enormously expensive procedure costing hundred-of-millions dollars, or around $28,000 - $90,000 per kilometre.

Great pains are needed to avoid coral reefs, shipwrecks and other obstructions, but even once cables are buried at the bottom of the ocean using high-pressure water jets, the challenges aren’t over. Global connectivity is regularly endangered by everything from marine life, to human activity and natural disasters.

Whether a subsea cable is damaged by a stray anchor, a volcanic eruption, or the gnawing of a curious shark, specialised ships must track down the problem and hoist up the line using robotic submersibles or grapnels so it can be repaired. This process never stops; transatlantic cabling alone typically demands more than 50 repairs a year.

Deluged by data

Today, digital content is flowing to more people in more places than ever before. With the rise of high-resolution video, social media and online gaming, global IP traffic is skyrocketing. We’re set to see 2.3 zettabytes (or more than 2 trillion gigabytes) running over global networks by 2020, a figure that’s ninety-five times the volume of the whole Internet in 2005.

While submarine cables are the only game in town for international connectivity, far outstripping the latency and throughput of satellites, cable-laying must continue at pace to match the world’s insatiable appetite for data. So-called ‘dark’ cabling is constantly being deployed that can be ‘lit’ as existing lines reach end-of-life.

So vital is subsea cabling in supporting today’s data deluge that even content producers are entering the infrastructure fray. To power their booming services, cloud companies, social platforms and media businesses are all investing in subsea cabling to ensure their content distribution networks can give customers fast, reliable connections. Microsoft and Facebook recently joined forces to lay their MAREA cable - expected to be the highest capacity transatlantic link ever created – while Google has just completed its $300m ‘Faster’ cable system, connecting the US West Coast and Japan.

In the future, the growing demand for high-capacity global connectivity may see other service providers and technology brands step into the infrastructure world, perhaps changing the nature of the Internet as we know it today.

Digital lifelines

With the world now totally reliant on ubiquitous digital services, redundancy and resilience are the name of the game when it comes to subsea cabling. We’ve already seen examples of what can happen when things go wrong.

In December 2006, the Hengchun earthquake severed nine of the eleven cables running through the Luzon Strait between Taiwan and the Philippines. Taiwan found itself without Internet connectivity, while half of Hong Kong's Internet capacity instantly disappeared, causing massive disruption to financial institutions across the Asia-Pacific region for some 49 days before repairs could be completed.

Although rare, incidents like Hengchun have pushed governments and infrastructure companies to find ever more ingenious ways to safeguard the world’s subsea connectivity.

New disaster-resilient designs now include a back-up cable along with the primary line. While this approach does require more upfront investment, it can save millions of dollars in the event of a problem. In the future, we may even see fleets of underwater drones conducting repairs autonomously as issues are detected.

Meanwhile, scientists and engineers continue to innovate with new phase modulation techniques and improvements in submarine line terminal equipment that have boosted throughput 80-fold in recent years. With subsea cables increasing in number and adding greater capacity, the resilience of the entire system inevitably increases.

Resilience is also being built into the Web outside of the water. Internet peering is designed to operate as a mesh with capacity on many different systems so that traffic distribution can failover to alternative routes if one subsea cable is damaged, minimising any noticeable impact on latency and performance.

As the world becomes ever more interconnected and data dependent, the subsea cabling we depend on will only grow stronger, more interwoven and more reliable. A hundred years from now, we’ll look back on today’s infrastructure as just a drop in the ocean.