Li-Fi - Internet connection using a light source

Many of us now connect our laptops and mobile devices to the internet via Wi-Fi and over mobile phone networks using radio waves. Could we one day use visible light sources to connect to the Internet? Technology known as Li-Fi was demonstrated by Dr Harald Haas at the TEDGlobal conference this summer.

Using LED light bulbs which can be made to flicker with great precision faster than the human eye can detect, it is possible to transmit data at up to an amazing 800 megabits per second (faster than is possible with Wi-Fi). Dr Haas demonstrated the transmission of a high definition video stream using a (specially augmented) desk lamp shining what appeared to be an uninterrupted beam of light.

There are certain obvious disadvantages to using light in this way. One is that it cannot travel through brick walls in the same way as radio waves, and any direct connection would have to be with other devices within sight. However, that same characteristic has a security advantage over Wi-Fi and cellular radio waves in that direct communications could not be intercepted from out of sight of the device. The same encryption methods could be used that are currently used for radio.
The technology could even be used in virtual darkness, as the light can be turned down to the point where it in undetectable by the human eye and still work.

There are a number of other potential advantages, for example energy efficiency and the fact that the spectrum of visible light is 10,000 time larger than that of radio waves.

Dr Haas paints a picture of a world where every lamppost is a wireless access point, cars exchange information through their headlights and tail lights to help prevent accidents, and wireless internet access is available in places where the use of radio waves would be unsafe. Time will tell.

Visible light is not going to replace radio waves for wireless communications, but it could well complement existing technologies in a very useful way.