Facebook researchers develop laser-based wireless communications

The research team at Facebook's Connectivity Lab has developed a new technology that can make wireless communications possible through laser light which is a far superior technology than the ones based on radio frequencies or microwaves.

The breakthrough could pave the way for fast optical wireless networks capable of delivering internet service to remote areas. "A large fraction of people don't connect to the internet because the wireless communications infrastructure is not available where they live, mostly in very rural areas of the world," says Tobias Tiecke, who led the research team.

This new Light-based wireless communication technology, also called free-space optical communications, offers a promising way to bring the internet to such areas where optical fibers and cell towers can be challenging to deploy in a cost-effective way.

Using laser light to carry information across the atmosphere can potentially offer very high bandwidths and data capacity, but the real challenge was how to precisely point a very small laser beam carrying the data at a tiny light detector that is some distance away.The Facebook researchers used fluorescent materials instead of traditional optics to collect light and concentrated it onto a small photodetector.

They combined this light collector, which featured 126sq cm of a surface that can collect light from any direction, with existing telecommunications technology to achieve data rates of more than 2 gigabits-per-second (Gbps).

"We demonstrated the use of fluorescent optical fibers that absorb one color of light and emit another color. The optical fibers absorb light coming from any direction over a large area, and the emitted light travels inside the optical fiber, which funnels the light to a small, very fast photodetector," Tiecke said in a paper described in the journal Optica.

The new light collector uses plastic optical fibers containing organic dye molecules that absorb blue light and emit green light. This setup replaces the classical optics and motion platform typically required to point the light to the collection area.

The fast speeds are possible because less than two nanoseconds lapse between the blue light absorption and the green light emission. In addition, by incorporating a signal modulation method called orthogonal frequency division multiplexing, or OFDM, the researchers transmitted more than 2 Gbps despite the system’s bandwidth of 100 MHz.