Rare earths enable record internet speeds

With a boost from fiber optic cables laced with rare earths such as erbium and thulium, researchers at Japan's National Institute of Information and Communications Technology were able to transmit 319 terabits of data per second over cables stretching 3,001 kilometers (1,865 miles), crushing any previous records in speed over such a long distance.

This not only smashes the previous record of an already jaw-dropping 178 Tb/s, according to NCIT, the technology is also compatible with existing infrastructure, which means that it could be upgraded relatively easily.

The new record was set by a team of scientists and engineers led by physicist Benjamin Puttnam of NICT and builds on previous work in which the institute participated, achieving speeds of 172 Tb/s.

The earlier high-speed achievement used a coupled three-core optical fiber, a technology that channels data along three optical fiber tubes rather than one as is currently standard, to reduce signal distortion over long distances. The 319-terabit speed uses similar technology but with four cores.

The data transmission uses a technology called wavelength-division multiplexing (WDM), which is beamed from a laser that splits the signals into 552 channels and sends it down the four optical fiber cores.

At 70-kilometer (43.5 mile) intervals along the fiber, amplifiers boost the strength of the signal to keep transmission loss at a minimum over long distances. These two new kinds of amplifiers are doped with the rare earth elements thulium and erbium.

Rare earth-doped fiber is an optical fiber in which ions of a rare earth element, such as neodymium, erbium, or holmium, have been incorporated into the glass core matrix, yielding high absorption with low loss in the visible and near-infrared spectral regions.

These ions absorb pump light (the process of raising electrons from a lower energy level in an atom or molecule to a higher one), typically at a shorter wavelength than the laser or amplifier wavelength, which excites them into stable levels.

Rare earths are ideal for this kind of technology as the ions found in certain rare earth elements show many absorption and fluorescence transitions in almost every region of the visible and near-infrared range. This means they can receive specific wavelengths more easily.

For the success of such speeds over such long distances, the innovation of its earlier multi-core design as well as the natural properties of rare earths allowed for the signal to daisy chain, getting a boost from the doped amplifiers with little to no loss of bits.

Overall, the average data rate per channel was around 145 gigabits per second for each core and around 580 Gb/s per second for all four cores combined, which is still more than the average internet service provider on a good day.

The cladding for the four optical fiber cores together has the same diameter as standard single-core optical fiber, which "is attractive for early adoption of SDM fibers in high-throughput, long-distance links, since it is compatible with conventional cable infrastructure and expected to have mechanical reliability comparable to single-mode fibers," NICT noted in its press release.

The team plans to continue work on their long-distance data transmission system, to try to both increase transmission capacity, and extend the transmission range.

So, how fast is 319 Tb/s theoretically? In a crucial test under optimum conditions, downloading the massive 220 GB package of Call of Duty: Black Ops Cold War – one of the largest download sizes of any video game to date – would take 0.005552 seconds.

If you aren't a fan of games and that number doesn't register with you, many reports have said that at 319 Tb/s, one could download 57,000 full-length movies in one second or the entire 70 million song library of Spotify in less than three seconds, that's 10 years of movies or nearly 500 years of music in the blink of an eye!