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Undersea Communication Cables

As you might already know, water covers 71% of the Earth. The distances across our oceans are vast, to put it mildly. Cornwall, at the south-western edge of Britain, to New York City is roughly 5,278km (3,280 miles). A journey from Japan in the far-east to California in the far-west across the International Dateline is mammoth 8,884 km (5,520 miles). These are distances that, until fairly recently, used to take people months to travel. Now with modern technology communication is done in the blink of an eye. However, something many might not be aware of, much of our information still travels across our oceans. Or should I say, across the ocean floor. 

Undersea communication cables is one topic that rarely seems to come up in conversation. But what if I told you that below the choppy waters of our oceans, seas and lakes lies an extraordinary 1.2 million kilometres (745,645 miles) worth of communication cables. If you’re having difficulty putting that kind of number in context, that’s roughly three times the distance from the Earth to the moon. 

In our modern, digital world you might be excused in thinking that information transferred electronically simply shoots out from our computer and magically finds its recipient thousands of miles away. But this is just not the case, in fact, 99% of international communication uses fibre optic cables, most of which lies underwater. 

Cables and our Lives

Before we get into the history surrounding the undersea cables, we’ll start with a little more information about the current cables that link our world. Modern cables are normally 25 millimetres (0.98 in) in diameter and weigh roughly 1.4 tonnes per kilometre (2.2 tons per mile).  

Submarine cable map
Submarine cable map by cable data by Greg Mahlknecht , map by Openstreetmap contributors is licensed under CC-BY-SA

If you look at a submarine cable map you will see that they go absolutely everywhere. Relatively isolated places might only have one cable running through it, but other areas, like the west of Europe and the Eastern United States, are linked with 5, 10 and even more cable lines.  

As I’ve just mentioned, almost all of our communication travels through these cables. From telephones calls to internet connections. If you’re beginning to think this sounds a little old fashioned what with the thousands of satellites we currently have, it comes down to cost and speed. Information travelling along the undersea cables is travelling at roughly 99.7% the speed of light and while the initial expense of laying the cables can be high, in the long run, it is significantly cheaper than using satellites. As of 2018, about half of the cables around the world were owned or leased by Google, Facebook, Amazon and Microsoft, with the rest owned by various telecommunication companies or consortiums.  

The First Cable

We’re only going to briefly mention the first undersea cable, not because it wasn’t an extraordinary achievement but because we have already covered an entire video on it here on Megaprojects.

15th President of the United States
James Buchanan

The first Transatlantic communication cable was laid in 1858 after years of difficulty. For the first time in history, two people on different continents were able to communicate. The first of which were Queen Victoria and U.S President James Buchanon – although the rate of speed was agonizingly slow and took 16 hours to deliver a short message. 

If you’re interested in more information on the first cable then check out the video on it – it is quite the tale of Victorian-era daring and ingenuity.   

The All Red Line

The last few decades of the 19th Century and into the 20th saw a boom in undersea communication cables. As the preeminent global power at the time it was Britain who led the way and the British Empire was linked by the ‘all red line’ which circumnavigated the globe without needing to land anywhere that wasn’t under the direct control of the British crown. 

This line effectively linked Britain with Barbados, South Africa, India, Australia, New Zealand and finally Canada before heading back across the Atlantic to Britain. While it would be wrong to suggest that the laying of any of these many cables was easy, by far the most challenging, and daunting, was the cable that crossed half of the Pacific Ocean from Fanning Island to British Columbia in Canada. This was the final section of the All Red Line which was officially completed in 1911 for £2 million (which works out at a huge £237 million today)    

Elsewhere, Hawaii was linked to the mainland United States in 1902, while Guam and the Philippines were linked the next year. At this point, every continent on the planet was now linked by undersea cables, except for Antarctica. Surely, this newfound connectivity would herald in a glorious era of friendship and cooperation. 

World War I

Or not. 

No sooner had Britain declared war on Germany, in response to its declaration of war on France, the British government ordered the immediate sabotage of all Germany communication lines. On 5th April 1914, a ship named The Alert, slipped quietly out of Dover before proceeding to an area of the English channel. It was here that their captain ordered hooks lowered and the dredging of the seabed to begin. After just a few hours, all five of Germany’s undersea cables had been severed, and their private connections to the world were gone.  

I say private because they could still use the British communication lines, which is exactly what the British had hoped for. The UK sent 400 censors to its distant outposts, along with 180 that remained in Britain, to monitor communication traffic moving along the communication lines. Throughout the entire war, as many as 80 million messages were subjected to some kind of censorship. 

Perhaps the most tantalising piece of information to be intercepted was the so-called Zimmerman telegram in which Germany offered Mexico U.S land in exchange for a military alliance. Unsurprisingly the British government gleefully revealed the telegram to the U.S administration, an act that no doubt sped-up American involvement in World War I. 

Cold War 

But this was still a small fry compared to what the Americans pulled off during the Cold War. If you’ve been following along with Megaprojects you may have seen our video on Project Horizon in which the U.S game fully attempted to salvage a Soviet submarine from the Pacific floor. It didn’t exactly work, but it showed that the Americans were willing to go to extreme measures to gain the upper hand during the Cold War. 

Operation Ivy Bell was another high-stakes gamble – but this one they did pull off. In the early 1970s, the U.S government discovered the existence of an undersea cable linking Vladivostok on the far east coast of the Soviet Union with Soviet Pacific Fleet naval base at Petropavlovsk on the Kamchatka Peninsula further north. 

To most of us, the idea of sending a submarine and divers down to the frigid depths of the Pacific to try and wiretap the Soviets might sound absurd. But this was the Cold War, and absurd was the name of the game. In October 1971, USS Halibut, (which incidentally was also the submarine involved in locating the lost Soviet Submarine involved in Project Horizon) travelled to the area under the guise of attempting to retrieve parts of a Soviet cruise missile. This part was actually true, but while they were there they also sent divers down to the Soviet cable who carefully wrapped a listening device around it.

Each month divers would return to retrieve the tapes, which were then sent on to the NSA. Astonishingly this went on for 10 years until a disgruntled veteran of the NSA, Ronald Pelton, who was knee-deep in debt ($65,000 – $202,000 today to be exact) began passing information to the Soviet Union. The Americans had been rumbled, and the recording device was finally removed and would eventually appear at the Great Patriotic War Museum in Moscow.

Fibre Optic Arrives 

Fibre optic cables arrived in the 1980s and it spawned an entirely new generation of undersea cables. Fibre optic is essentially a flexible fibre made of either drawing glass or plastic which is normally only slightly thicker than a human hair. 

The first cable to use such technology was the TAT-8 transatlantic communication cable which connected the United States with Britain and France for $335 million ($736 million today) and was completed in 1988. The TAT-8 included two working pairs of fibres and one back-up pair and was capable of carrying 280 Mbit/s (40,000 telephone circuits) across the ocean. 

Though there were a few hiccoughs down to manufacturing defects which meant the first two years were not quite a smooth sailing as had been hoped, by and large, it was a great success. So much so that it reached its operating capacity within 18 months, which was considerably less than the decade that had been expected. 

But this was almost certainly because of what had appeared on the horizon that would forever change our world. The success of the TAT-8 encouraged IBM to construct a dedicated transmission system between Cornell University in New York State and the European Organization for Nuclear Research (CERN) in Switzerland which was completed in February 1990. With this in place, a high speed, constant connection was made between the early U.S and European versions of the internet. Ten months later, we had our first demonstration of the World Wide Web.    

Modern Day     

Which brings us more or less up to the modern-day. The introduction of fibre optic cable set off a mad dash as similar cables began appearing all over the world. Between 1999 and 2001 alone, the cable industry spent roughly $22 billion (32.3 billion today), and the same period saw the balance of where cables had mostly been laid up to that point begin to shift.  

Considering how important trade between Europe and the U.S has traditionally been, it’s no surprise that the majority of new cables ran across the Atlantic Ocean. But between 1998 and 2003, 70% of new cables being installed ran across the Pacific Ocean, as the U.S began to pivot in that direction. It wasn’t until 2009 that East Africa was finally plugged into the chain with an underwater cable that ran from Mtunzini in South Africa to Marseille in France with landing points in Djibouti, Kenya, Tanzania and Mozambique – as well as an extension east to India. The total cost of the line was believed to be in the region of $650 million ($787 million today).

At this point, you might be wondering just how all of this cable is laid. Once a decision is made to lay a cable, a scouting ship will first map out a route. Ideally, they want the cable to run along flat parts of the ocean while avoiding coral reefs, shipwrecks and anything else that might snag a cable. 

Cable layer ship
Cable layer ship by Nsandel is licensed under CC-BY-SA

After the scouting run has been completed, a specially designed boat called a cable layer can begin from a landing station. This is the point where the cable is connected on land and will normally continue out into the ocean where it is spliced with the cable on the ship. These boats can carry up to 2,000 km (1,242 miles) worth of cable and once they are out to sea they can cover quite a distance per day, anywhere between 100km and 200km (62 to 124 miles). After reaching their destination, the cable can be spliced with cable at another landing station. And hey presto, you have an undersea communication cable.

While the fibre optics themselves are very small, they are wrapped in several layers that bring the thickness up to roughly the diameter of a garden hose. The optical fibres in the centre are followed by a layer of petroleum jelly, a copper or aluminium tube, polycarbonate, an aluminium water barrier, stranded steel wires, mylar tape (used in everything from nail polish to kites) and finally polyethene.      

Dangers to the Cables

Now and again a new story pops up telling how a certain area of the world has experienced a decrease in internet speed, or even an outage, because of a problem with these cables and these are more common than you’d think – there are more than 50 repairs in the Atlantic Ocean per year alone. We don’t often notice it because most countries are now linked by multiple cables, so even if one goes down it doesn’t significantly affect service.  

These are quite delicate cables travelling thousands of miles and a lot can happen in that distance. As we’ve already seen, sometimes it is down to rival foreign power, though it must be said this is incredibly rare today. Sharks have been known to take a liking to undersea cables, possibly because they are attracted to the electrical current, and sometimes gnaw straight through the cable. Earthquakes can also have a huge impact, as did the 2006 Hengchun earthquakes which rocked the South China Sea on 26th December 2006. While luckily only two people died because of the earthquake itself, the resulting internet outage was severe and affected China, the Philippines, Taiwan and Hong Kong. 

But it’s not just sharks with an electrical fetish and natural disasters that we need to worry about. In March 2007, pirates stole 11 km (7 miles) worth of a cable that linked Thailand, Vietnam, and Hong Kong. It resulted in internet users in Vietnam experiencing much slower internet speeds than normal. Oh, and by the way, the thieves tried to sell the 100 tons of cable for scrap, but were apprehended by police. 

Diver Checking Underwater Protection of Cable
Diver Checking Underwater Protection of Cable by The Official CTBTO Photostream is licensed under CC-BY

Often cable breakages remain a mystery, but still, need repairing nonetheless. The operators of the cables can normally detect where a breakage is because of electrical measurement. A cable repair ship is then dispatched to the area and using hooks (not much has changed in a hundred years) the crew fishes the cable out of the water. Most damaged cables are repaired by adding a spliced section to both ends, which creates a slightly longer cable than before, so the additional length is left in a U shape on the ocean floor. 

What Next?

I would be willing to bet that in 100 or 200 years people might look back and laugh at us physically laying cables from continent to continent. Even now, it sounds a little old fashioned but that’s just where we are with communication these days. 

Once you get past the slightly odd notion of 1.2 million kilometres (745,645 miles) of cable linking the world, you can only marvel at this quite astonishing feat that we as humans have managed to achieve. Looking at an undersea cable map it is simply astonishing just how many lines there are, but when you consider the level of speed and connectivity we have come to expect, you begin to understand why it’s all needed. But where do we go from here?

In 2013 the internet traffic per capita was 5 gigabytes, as of 2020, the number has reached 21 gigabytes. Our need for speed and our rate of consumption is growing exponentially, but surely there will come a point when we just can’t throw any more cables across the oceans. 

Our undersea communication cable network is something few pay any attention to. We give very little thought to how exactly you can send an email from Britain to Patagonia or from Alaska to Zanzibar in a matter of seconds. Our thought on the matter tends to stop a fraction of a second after we hit send and we quickly move on. But perhaps we should stop and consider this for a moment, that our immediate connectivity is actually thanks to the hundreds of thousands of miles worth of cable that stretch around our world. The world indeed feels a lot smaller now because of the ease in which we can communicate, but physical distances haven’t changed. Those many miles still needed to be painstakingly laid and carefully maintained. 

To put things in perspective, the next time you send an email across an ocean, picture that email travelling thousands of miles at close to 1 billion km/h (670 million mph), up to 8km (4.9 miles) below the surface of the ocean. You might not think about emails in quite the same way again.        

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