ETH Zurich sent 'tens of gigabits' of data through air using lasers

ETH Zurich and its partners have sent large amounts of data using lasers between the mountain peak, Jungfraujoch, and Bern.
Christopher McFadden
The test brings us one step closer to using laser for telecommunications over long distances.

ETH Zurich 

ETH Zurich scientists have successfully transmitted several tens of terabits of data per second using lasers in Switzerland. Developed with other European technology partners, this marks a significant milestone towards one day repeating the trick at scale using a network of low-Earth orbit satellites. It could also mean that conventional and expensive undersea telecommunication cables could become a thing of the past.

Called the European Horizon 2020 project, the test was conducted between the mountain peak, Jungfraujoch, and the city of Bern in Switzerland. The project partners tested the laser system by transmitting data over 33 miles (53 kilometers).

Lasers would be cheaper than cables

The internet's foundation is supported by a complex web of fiber-optic cables, carrying over 100 terabits of data per second (1 terabit = 1012 digital 1/0 signals) between nodes. Intercontinental connections are established through expansive deep-sea networks with a hefty price tag - a single cable across the Atlantic can cost hundreds of millions of dollars. According to some sources, like TeleGeography, there are currently 530 active undersea cables, with the number continuing to increase.

But, there are expensive, labor, and time-consuming to deploy. Wireless telecommunications would be far simpler and cheaper. A fact that is the foundation of SpaceX's groundbreaking Starlink constellation. However, Starlink uses radio waves considerably weaker than electromagnetic waves like light or infrared. Optical systems that use laser technology operate in the near-infrared range with much shorter wavelengths, measuring only a few micrometers. This enables them to transmit significantly more information within a given period than other systems.

However, using lasers comes with its challenges, too, namely interference from the molecules of the atmosphere. The lead author of the study, Yannik Horst, who is a researcher at ETH Zurich's Institute of Electromagnetic Fields, explained that the test route between the High Altitude Research Station on Jungfraujoch and the Zimmerwald Observatory at the University of Bern was more challenging than between a satellite and a ground station, making it an impressive achievement for optical data transmission.

As the laser beam travels through the dense atmosphere closer to the ground, it encounters various factors that affect the movement of light waves and data transmission. These factors include turbulent air over high snow-covered mountains, the water surface of Lake Thun, the densely built-up Thun metropolitan area, and the Aare plane. Additionally, the shimmering of the air caused by thermal phenomena disrupts the uniform movement of light, which can be observed by the naked eye on hot summer days.

However, the team overcame this with a special chip and almost 100 tiny adjustable mirrors. According to Horst, the mirrors can correct the phase shift of the beam at its intersection surface by measuring the gradient 1,500 times per second. This results in an impressive improvement of the signals by a factor of around 500.

The system could be scaled to 40 channels

“Our system represents a breakthrough. Until now, only two options have been possible: connecting either large distances with small bandwidths of a few gigabits or short distances of a few meters with large bandwidths using free-space lasers," explained ETH Zurich’s Institute of Electromagnetic Fields, headed by Professor Jürg Leuthold.

It is worth noting that a remarkable performance of 1 terabit per second was attained using just one wavelength. As for its practical use, the system can be conveniently expanded to 40 channels by utilizing standard technologies, enabling it to achieve a whopping 40 terabits per second.

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