Google says the fiber-optic cable it’s building across the Atlantic Ocean will be the fastest of its kind. When the cable goes live next year, the company estimates it will transmit around 250 terabits per second, fast enough to zap all the contents of the Library of Congress from Virginia to France three times every second. That’s about 56 percent faster than Facebook and Microsoft’s Marea cable, which can transmit about 160 terabits per second between Virginia and Spain.
Fiber-optic networks work by sending light over thin strands of glass. Fiber-optic cables, which are about the diameter of a garden hose, enclose multiple pairs of these fibers. Google’s new cable is so fast because it carries more fiber pairs. Today, most long-distance undersea cables contain six or eight fiber-optic pairs. Google said Friday that its new cable, dubbed Dunant, is expected to be the first to include 12 pairs, thanks to new technology developed by Google and SubCom, which designs, manufactures, and deploys undersea cables.
Dunant might not be the fastest for long: Japanese tech giant NEC says it has technology that will enable long-distance undersea cables with 16 fiber-optic pairs. And Vijay Vusirikala, head of network architecture and optical engineering at Google, says the company is already contemplating 24-pair cables.
The surge in intercontinental cables, and their increasing capacity, reflect continual growth in internet traffic. They enable activists to livestream protests to distant countries, help companies buy and sell products around the world, and facilitate international romances. “Many people still believe international telecommunications are conducted by satellite,” says NEC executive Atsushi Kuwahara. “That was true in 1980, but nowadays, 99 percent of international telecommunications is submarine.”
So much capacity is being added that, for the moment, it’s outstripping demand. Animations featured in a recent New York Times article illustrated the exploding number of undersea cables since 1989. That growth is continuing. Alan Mauldin of the research firm Telegeography says only about 30 percent of the potential capacity of major undersea cable routes is currently in use—and more than 60 new cables are planned to enter service by 2021. That summons memories of the 1990s Dotcom Bubble, when telecoms buried far more fiber in both the ground and the ocean than they would need for years to come.
But the current growth in new cables is driven less by telcos and more by companies like Google, Facebook, and Microsoft that crave ever more bandwidth for the streaming video, photos, and other data scuttling between their global data centers. And experts say that as undersea cable technologies improve, it’s not crazy for companies to build newer, faster routes between continents, even with so much fiber already laying idle in the ocean.
Controlling Their Own Destiny
Mauldin says that although there’s still lots of capacity available, companies like Google and Facebook prefer to have dedicated capacity for their own use. That’s part of why big tech companies have either invested in new cables through consortia or, in some cases, built their own cables.
“When we do our network planning, it’s important to know if we’ll have the capacity in the network,” says Google’s Vusirikala. “One way to know is by building our own cables, controlling our own destiny.”
Another factor is diversification. Having more cables means there are alternate routes for data if a cable breaks or malfunctions. At the same time, more people outside Europe and North America are tapping the internet, often through smartphones. That’s prompted companies to think about new routes, like between North and South America, or between Europe and Africa, says Mike Hollands, an executive at European data center company Interxion. The Marea cable ticks both of those boxes, giving Facebook and Microsoft faster routes to North Africa and the Middle East, while also creating an alternate path to Europe in case one or more of the traditional routes were disrupted by something like an earthquake.
Cost Per Bit
There are financial incentives for the tech companies as well. By owning the cables instead of leasing them from telcos, Google and other tech giants can potentially save money in the long term, Mauldin says.
The cost to build and deploy a new undersea cable isn’t dropping. But as companies find ways to pump more data through these cables more quickly, their value increases.
There are a few ways to increase the performance of a fiber-optic communications system. One is to increase the energy used to push the data from one end to the other. The catch is that to keep the data signal from degrading, undersea cables need repeaters roughly every 100 kilometers, Vusirikala explains. Those repeaters amplify not just the signal, but any noise introduced along the way, diminishing the value of boosting the energy.
You can also increase the amount of data that each fiber pair within a fiber-optic cable can carry. A technique called “dense wavelength division multiplexing” now enables more than 100 wavelengths to be sent along a single fiber pair.
Or you can pack more fiber pairs into a cable. Traditionally each pair in a fiber-optic cable required two repeater components called “pumps.” The pumps take up space inside the repeater casing, so adding more pumps would require changes to the way undersea cable systems are built, deployed, and maintained, says SubCom CTO Georg Mohs.
To get around that problem, SubCom and others are using a technique called space-division multiplexing (SDM) to allow four repeater pumps to power four fiber pairs. That will reduce the capacity of each pair, but cutting the required number of pumps in half allows them to add additional pairs that more than makes up for it, Mohs says.
“This had been in our toolkit before,” Mohs says, but like other companies, SubCom has been more focused on adding more wavelengths per fiber pair.
The result: Cables that can move more data than ever before. That means the total cost per bit of data sent across the cable is lower.
Corrected, 4-5-19, 3:50pm ET: An earlier version of this story misstated the technology that allowed Google and SubCom to add more fiber pairs to a cable.