Alphabet’s laser web system despatched 700TB of knowledge with 99.9% availability
A transmitter from Project Taara.
Both ends can adjust their mirrors for a perfect connection.
Radiant over the Congo River.
Aerial view of Brazzaville, with the Congo River and Kinshasa, the capital of the Democratic Republic of the Congo, in the background.
Educational pictures / universal picture group
A line drawing shows the large heat sink on the back.
Google’s parent company, Alphabet, is still experimenting with connecting remote cities to the internet using laser beams. Today Alphabets Moonshot “X Lab” shared an update on Project Taara, its experimental point-to-point optical communication system, often referred to as “fiber optic without fiber”. The company has built a working installation in Africa and blasted a 20 Gbit / s connection across the Congo River of around 5 km to a city of millions in order to reduce the cost of Internet access.
The Taara laser beam bridges the gap between Brazzaville in the Republic of Congo and Kinshasa in the Democratic Republic of the Congo, which are on opposite sides of the Congo River. Brazzaville has decent internet, but because no one wanted to run a fiber optic line through the deepest and second fastest river in the world, Kinshasa is using a fiber optic line that runs 400 km around the river, and the internet is five times more expensive there. Alphabet’s 20 Gbps commercial link has now been up and running for 20 days, and the company says it has served nearly 700 TB of data with 99.9 percent availability in that time.
Taara was born from the Internet balloon project “Loon”, which started in 2017. Google originally built flying cell towers to beam the Internet down from the sky (via RF), but for balloon-to-balloon backhaul, the company planned to use laser beam communications. Space X has just started doing something similar by equipping its Starlink satellites with space lasers for optical communication between the satellites. One advantage of sky- and space-based laser communication is that a point-to-point optical beam cannot interfere much. With ground-based lasers, there is more interference to consider as they have to deal with almost everything: rain, fog, birds, and once, according to Alphabet’s blog post, “a curious monkey”.
Much of the Taara project revolved around solving all of these ground-based interference problems. Taara shoots a laser into a 45-degree mirror, resulting in a laser that makes a 90-degree turn and fires out of the front lens. The mirror is movable so that both ends of Taara can make small adjustments. Alphabet says, “To establish a connection, Taara’s terminals look for each other, recognize each other’s light beam and lock in like a handshake to establish a high-bandwidth connection.” Alphabet says that with adjustable bars it could handle haze, light rain, and birds without interrupting operations.
Like any other method of connecting to the Internet, Alphabet says wireless optical communication isn’t a one-size-fits-all solution, but it can fill the gaps where faster, more reliable methods (like fiber optics) are not possible. With local weather being a primary nuisance, the company has created a color-coded map of the world where the technology is workable. Oddly enough, red is good here, indicating that with a link in this area, Alphabet expects 99 percent availability.