Lasers enable internet backbone via satellite

The researchers tested data transmission by laser over 53 kilometres from the Jungfraujoch to Zimmerwald near Bern ETH Zurich

Using lasers, scientists have transmitted several terabits of data per second, despite a huge amount of disruptive air turbulence, between the Jungfraujoch mountain peak and the Swiss capital, Bern.

This will soon eliminate the need for expensive deep-​sea cables, researchers from Swiss federal technology institute ETH Zurich said in a statementExternal link on Tuesday.

The backbone of the internet is formed by a dense network of fibre-​optic cables, each of which transports up to more than 100 terabits of data per second between the network nodes. The connections between continents take place via deep sea networks – which is an enormous expense: a single cable across the Atlantic requires an investment of hundreds of millions of dollars.

Soon, however, this expense may drop substantially. Scientists at ETH Zurich, working together with partners from the space industry, have demonstrated terabit optical data transmission through the air in a European Horizon 2020External link project. In the future, this will enable much more cost‑effective and much faster backbone connections via near-​earth satellite constellations, they said.

To achieve this milestone, the project partners took a significant leap forward in establishing a satellite optical communication link through a successful test conducted between the alpine mountain peak, Jungfraujoch, and the city of Bern. Although the laser system was not directly tested with an orbiting satellite, they accomplished high-​data transmission over a free-​space distance of 53km.

“For optical data transmission, our test route between the High Altitude Research Station on the Jungfraujoch and the Zimmerwald Observatory at the University of Bern is much more challenging than between a satellite and a ground station,” said Yannik Horst, the study’s lead author and a researcher at ETH Zurich’s Institute of Electromagnetic Fields.

The laser beam travels through the dense atmosphere near the ground. In the process, many factors – diverse turbulence in the air over the high snow-​covered mountains, the water surface of Lake Thun, the densely built-​up Thun metropolitan area and the Aare plane – influence the movement of the light waves and consequently also the transmission of data. The shimmering of the air, triggered by thermal phenomena, disturbs the uniform movement of light and can be seen on hot days by the naked eye.

More information per unit of time

Internet connections via satellite are not new. However, transmitting data between satellites and ground stations uses radio technologies, which are considerably less powerful. Like a wireless local area network (WLAN) or mobile communications, such technologies operate in the microwave range of the spectrum and thus have wavelengths measuring several centimetres.

Laser optical systems, in contrast, operate in the near-​infrared range with wavelengths of a few micrometres, which are about 10,000 times shorter. As a result, they can transport more information per unit of time.

The performance of one terabit per second was achieved with a single wavelength. In future practical applications, the system can be easily scaled up to 40 channels and thus to 40 terabits per second using standard technologies.