The jungle book

Forget Loon’s balloon burst, we just shot 700TB of high-speed laser between two cities, says Google • The Register


Engineers at Google’s Moonshot X tech lab said they used lasers to broadcast 700TB of internet traffic between two cities separated by the Congo River.

The capital cities of the Republic of Congo and the Democratic Republic of the Congo, Brazzaville and Kinshasa, respectively, are only 4.8 km (about three miles) apart. Residents of Kinshasa, however, have to pay five times more than their neighbors in Brazzaville for broadband connectivity. This is apparently because the fiber backbone to Kinshasa has to carry over 400 km (250 miles) around the river – no one wanted to run the cable there.

There is a shorter route for the data to be taken between cities. Instead of transmitting information in the form of light through networks of cables, it can be beamed directly over the river by laser.

In an effort dubbed Project Taara, X built two terminals, one in Brazzaville and another in Kinshasa, to transmit and receive data encoded in beams of laser light.

“In the same way that traditional fiber uses light to carry data through cables in the ground, Taara’s wireless optical communication links use very narrow invisible beams of light to provide speeds similar to those of the fiber, ”explained Baris Erkmen, Director of Engineering for Taara today. .

“To create a link, Taara’s terminals search for each other, detect each other’s light beam and lock together like a handshake to create a high-speed connection.

Approximately 700 TB of data was exchanged over 20 days at speeds of up to 20 Gbps, with 99.9% availability, with the help of Econet – the multinational telecommunications giant, not the ‘old Acorn network system. The goal of the facility was to relay high-speed Internet traffic between cities more as an equipment test than anything else.

A lot of effort has been put into tracking and directing the light beam to a sensor a few miles away, and mitigating the effects of bad weather, interference from animals, etc.

Google diagram of the Taara project broadcasting broadband over a river

Google’s diagram of the Taara project transmitting broadband between two cities

X has experimented with wireless optical communication techniques using lasers in various projects over the years, including from high altitude balloons in the now defunct Loon unit. In the past, it was more difficult to maintain bandwidth connections over great distances. Small disturbances in weather conditions, fog or even birds flying through the laser beams were enough to interrupt internet service.

Erkmen said the latest terminals installed in the Republic of Congo and Democratic Republic of Congo have improved, however. They are able to adapt automatically and can rotate their internal mirrors or direct their sensors to adapt to changing conditions to maintain a direct connection between them.

“Imagine aiming at a beam of light the width of a wand precise enough to hit a target 5 centimeters (about the size of a quarter of the United States) that is ten kilometers away; that’s how precise the signal has to be to be strong and reliable, ”he said.

X has already tested its wireless optical communication technology in India and Kenya as well. The register asked X for more information. ®


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