German researchers use LEDs for wireless data transmission

In the future, getting a broadband connection might be as simple as flipping on a light switch, according to a group of German researchers who say the light coming from the lamps in your home could one day encode a wireless broadband signal.
"The advantage is that you'd be using light that is already there," says Jelena Vucic of the Fraunhofer Institute for Telecommunications, Heinrich-Hertz-Institute in Berlin, Germany.
Vucic and her colleagues have found a way to get the most from this synergy of illumination and information. Researchers at the Fraunhofer Institute for Telecommunications at the Heinrich-Hertz Institute experimented with using visible light from commercial light-emitting diodes to carry data wirelessly at speeds of up to 230Mbit/sec.
Research into wireless data communications using LEDs has been going on for years, but the 230Mbit/sec speed is considered a record when using a commercial LED.
Vucic said the advantage in using light to carry data over Wi-Fi or another system is that the lights are already in a room. The team built a visible wireless system in their lab to download data at 100Mbit/sec and then upgraded the system to get 230Mbit/sec. Although state-of-the-art radio wireless can achieve comparable speeds, Vucic says they should be able to double their data rate again by employing a more sophisticated modulation signal.
As of now, the majority of wireless in homes and businesses is achieved through a radio frequency WiFi connection. But WiFi has limited bandwidth and it is unclear where to find more in the already-crowded radio spectrum. By contrast, visible-frequency wireless has all the bandwidth one could want, according to the Optical Society of America. The signal would be generated in a room by slightly flickering all the lights in unison.
No one would be bothered by this because the rate of modulation would be millions of times faster than a human eye can see. Since visible light can't go through walls like radio, there would be no unwanted interference from stray signals and less worry of outside hackers.
Incandescent and fluorescent bulbs can't flicker fast enough, so all the lights would have to be LEDs. Although commercial LEDs have a limited bandwidth of only a few MHz, Vucic and her colleagues were able to increase this bandwidth tenfold by filtering out all but the blue part of the LED spectrum.