Langer, operating at Berlin’s Heinrich Hertz Institute, a branch of Fraunhofer Institute for Telecommunications, also accounted an earlier experiment that reached 100Mbit/s using only white-light LEDs. ”We turn the LEDs off and on in very rapid succession and transfer the information as ones and zeros,” he explained. “The modulation of the light is imperceptible to the human eye. On the receiving end is a simple photo diode, and circuitry that changes the diode’s signals into a digital data stream. According to Langer, advantages of this method admit the simplicity of changing the LEDs into signal-sending devices, and the riddance of cabling as a signal-transferring medium.
In the 100 Mbit/s experiment, the signalling LEDs were situated on the ceiling, and the transmission was error-free in an area of 10 square meters, received by a group of four photo diode–fitted laptops. HHI researcher, Anagnostis Paraskevopoulos said, ”We transferred four videos in HD quality to four different laptops at the same time.” Applying visible light as a signaling medium instead of radio waves has clear advantages in areas such as hospitals and aircraft where radio transmission is not possible and where cabling would be discouragingly expensive.
The most evident disadvantage of visible light communication (VLC) is that the signal can be easily barred by any solid object, for example a hand moving between the LEDs and the photo diode. The unfitness for light to penetrate walls also limits VLC to special-case scenarios. As limited as VLC may seem, when The Reg spoke in June with Aicha Evans, wireless engineering manager at Intel, she stated that “a lot of people are talking about visible light.”
Though Evans accepted that “it’s still science fiction,” VLC may very well show its value in the last few meters of a data stream. If at this early phase of its evolution it’s already being demonstrated at 800Mbit/s speeds, VLC may very well prove to be a functional high-speed, within-four-walls broacast WLAN in future executions.
Elektronology 
