GoKawiilWe treat the internet as if it were air, ambient and ownerless, when in reality, however, it is the exact opposite. This is a look at what connects the world, and who builds and owns that infrastructure.
At the northeastern edge of La Línea de la Concepción, on a scrubby Mediterranean beach called El Burgo–Torrenueva, there is an old battlement-tower, La Torre Nueva, and not much else. It was part of the system of coastal watchtowers during the 16th century that would defend the area against the incursion of the Barbary corsairs. The coordinates are 36°12′36″N, 5°19′27″W . Walk the tideline and you would never know that buried two metres beneath the sand, a fibre-optic cable comes out of the sea here and turns into the internet. It’s the start of a line that runs across the Strait of Gibraltar to Ceuta, on the African coast, and on toward two continents. Nearly everything you do online that crosses an ocean passes through a cable like this, ending, in most cases, underneath a similarly unremarkable patch of coast.
Note: Ceuta is an interesting place by itself, that has recently gained some attention and that would also make for an interesting write-up of its own. However, the tl;dr is that it is an autonomous Spanish city of some 85,000 people sitting on the North African coast, bordering Morocco, which means the European Union has one of its very few land borders with the African continent running straight through a peninsula most people could probably not even point to on a map. It has been held by the Spanish crown since 1668, it had been Portuguese before that, and Morocco seemingly never stopped claiming it. For our purposes, though, what matters is that the small enclave, until very recently, hung off the mainland’s network by a single ageing link.
When we talk about the internet we do so as if it were air. Ambient, ownerless, and everywhere. In reality, however, it is the exact opposite, because international data doesn’t (normally) travel by, let’s say, satellite, despite what most people might assume. It travels through roughly 1.5 million kilometres of very real (and very owned) fibre-optic cable lying on the seabed, surfacing at a small number of carefully chosen landing points.
For these landing points you normally need a gently sloping seabed, mild currents, and little marine traffic, so that anchors and trawlers don’t sever the line. Suitable spots are scarce enough that the same beach usually becomes the shared landfall for several cable systems at once.
Cables? What cables?
Unlike what you might be thinking of at first, submarine cables aren’t your run-of-the-mill Ethernet or fibre cable. The hardware that does the heavy lifting out in the deep ocean is about as thick as a garden hose with roughly 25mm across and weighing in at around 1.4 tonnes for every kilometre. The part that carries your data is a small bundle of glass fibres, each one around the same thickness as human hair, sitting in the very middle.
Everything else wrapped around those fibres is there to keep them alive in a deeply hostile environment. Working outward from the core, the fibres sit in a water-blocking gel inside a thin copper or aluminium tube, which is sheathed in polycarbonate, then an aluminium water barrier, then a layer of stranded steel wires that give the cable its tensile strength, then a wrap of mylar tape, and finally an outer skin of polyethylene. The copper is for power, because the cable doubles as a very long extension lead, which we will get to in a moment. Closer to shore, where trawlers and anchors roam, the whole thing gets one or two further jackets of galvanised steel armour wire, swelling it to 50mm or more in diameter and several times the weight. Hence, the cable that surfaces on our Spanish beach is buried a couple of metres down and not simply left lying on the sand.
The reason a copper conductor runs the entire length is that light, no matter how pure the glass, slowly fades as it travels, and so every 50 to 80 kilometres the cable is interrupted by a repeater, which is an optical amplifier that boosts the signal back up before passing it along. Each repeater needs electricity, and because the fish sadly still didn’t manage to install power sockets on the ocean floor, the shore stations at either end have to feed a direct current of anywhere between 3,000 and 15,000 volts down that copper core, to literally power the cable from both ends at once.
On top of the amplification, modern systems lean on a stack of clever tricks to keep the signal intelligible across thousands of kilometres of glass, including wavelength-division multiplexing to cram many separate colours of light down a single fibre, coherent detection to read them back out, and forward error correction to repair whatever gets garbled along the way.
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