Will the need for the costly construction of deep-sea cables soon be eliminated? If it is up to ETH Zurich scientists, the answer is yes! In an experiment presented in the science magazine “nature,” a Swiss-led international research team demonstrated what a future ultrafast satellite internet could look like.

I“In the future, this technology will make it possible to create backbone connections via near-Earth satellite constellations that are significantly less costly than deep-sea cables,” says a related ETH news release.

This is how it works: Unlike the Starlink satellite internet that has already been installed by Elon Musk’s SpaceX company and transmits data like a wireless local area network (WLAN) or mobile communications with wavelengths of several centimeters, the laser optical system operates in the so-called near infrared range with wavelengths that are about 10,000 times shorter. As a result of just that, they can transport clearly more information per unit of time. In addition, new robust light modulation formats were used in the project. They’re intended to massively increase detection sensitivity enabling high data rates even under the worst weather conditions or at low laser power. The laser beam is transmitted and received by telescopes with a diameter of several dozen centimeters. In the event of a phase shift due to external influences, a chip-sized electromechanical system with a matrix of 97 tiny adjustable mirrors corrects the shift 1,500 times per second.

Challenging test conditions in the Swiss Alps

The project partners did not test their laser system with an orbiting satellite but by data transmission across 53 kilometers (33 miles) from the Jungfraujoch mountain peak to Bern. “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,” explains Yannik Horst, the study’s lead author. Across the whole distance, the laser beam had to travel through the dense atmosphere near the ground. The wide range of turbulences 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 plain influenced the movement of the light waves and consequently also the transmission of data.

“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.”

Juerg Leuthold, leader of the research group

If and when the laser transmission system will find its way into space remains to be seen. Industry partners will carry out the practical implementation of the concept in a marketable product.