In one of the latest issues of The Economist, there was an interesting article about high-speed optical wireless. At the recent Consumer Electronics Show in Las Vegas, a few smartphones from Casio were presented. Their new feature is that they can exchange data and transmit digital signals by varying the intensity of the light given off their screens. These variations are imperceptible to the human eye, but the camera on another phone can detect it at a distance of up to ten metres. It seems a bit like going back to signal lamps and Morse code, doesn’t it? It’s actually the beginning of a fast and cheap wireless-communication system called Li-Fi.
Last October, the Li-Fi Consortium was formed. It is an industry group open to any company or organisation focused on the development and market introduction of optical wireless communication technology. Radio-based wireless is workable, the problem is that, with an ever increasing number of devices connected, only a limited amount of radio spectrum is available. Li-Fi offers the opportunity to exploit illumination, a completely different part of the electromagnetic spectrum which can be found almost everywhere.
Bulbs and tubes are not really suitable for modulation, but they are being replaced by LEDs, which are semiconductor devices. Producing flickering signals with their electronics is easy, according to Gordon Povey, who is working on light communication with Harald Haas and his colleagues at the University of Edinburgh.
The LEDs involved in Li-Fi would need photodetectors to receive data, but even if LEDs are not modified, hybrid systems are possible. For example, data could be downloaded using light but uploaded using radio. Moreover, light can also be used in areas which contain sensitive equipment that radio signals might interfere with, such as in aircraft and operating theatres.