Ray of light emerges for wireless capacity ©The University of Edinburgh/Laurence Winram Professor Harald Haas, pureVLC's chief science office Alexander Graham Bell is famous for inventing the telephone. But the Scots-born scientist actually thought his greatest achievement was the photophone, which sent its signal not through a wire, but along a beam of sunlight. The photophone never took off, but Harald Haas, chair of mobile communications at Bell's alma mater, the University of Edinburgh, believes that more than a century after its 1880 debut, light-based wireless is finally ready to shine. As co-founder and chief science officer for university spin-off PureVLC, Prof Haas is spearheading development of new technology, dubbed LiFi, that can turn standard light fittings into wireless data transmitters to rival the WiFi networks now ubiquitous in offices and homes. This month PureVLC shipped its first product, a £5,000 unit for a US healthcare provider. And on Friday the company will use a system it has installed at the Business Academy Bexley in London to stream a video address by Boris Johnson, the mayor of London. A key change from Bell's day is the introduction of light-emitting diode lights or LEDs, says Prof Haas in an interview in his office, appropriately located in the university's Alexander Graham Bell building. "The idea has got a whole new perspective," he says. LEDs are electronic circuits . . . and they bring entirely new opportunities. LEDs" brightness can be altered very rapidly, allowing them to transmit data at very high speeds to a photosensitive receiver. A PureLVC demonstration model set up for visitors easily streams high-quality video - at least until Prof Haas steps in front of the beam. But receivers can be made sensitive enough to read even indirect light, and the flickering involved is much too subtle to be detected by the human eye. Light-based transmission does have inherent limitations. Bell's photophone was crippled by reliance on sunlight - conversations could be cut by passing clouds - and its short range. LEDs are not weather dependent, but signals based on LiFi cannot penetrate walls or curtains. Yet backers say this can be an advantage - nobody can break into a network from outside its visual range. PureVLC's first customer is particularly interested in its ability to provide greater security than WiFi. Though Li-Fi networks will require some new infrastructure to link light fittings, Prof Haas says it can piggyback on the rapid introduction of LED fittings. And the technology allows more efficient use of capacity in buildings such as offices and schools, where each light fitting will stream data specifically for the users closest to it. The system to be tested at the Business Academy Bexley, for example, is intended to offer much greater connections speeds for each pupil. PureVLC, which next month changes its name to PureLiFi, is one of a number of companies hoping to tap light-based data transmission. Casio of Japan has developed applications allowing data exchanges between smartphones. France's Oledcomm said last month it had demonstrated LiFi-equipped street lights at a trade fair, paving the way for test installations. Research firm MarketsandMarkets says visual light communication technology will increasingly be used as a complement to WiFi and mobile phone data networks, with the total value of sales set to soar from $96m in 2012 to $6.14bn in 2018. Prof Haas says a main driver of future growth will be a looming network capacity crunch as data-heavy services such as video streaming clog available radio bandwidth. Cisco, the IT equipment and service provider, forecasts global mobile data traffic is set to grow to 11.2 exabytes a month by 2017, a 13-fold increase over 2012. PureVLC will seek to prove its technology by serving niche applications until the capacity crunch hits "in two or three years," says Prof Haas. "That is really where it will become imperative," he says. The fate of the photophone is a reminder of how new technologies can falter. But the Bavarian professor thinks LiFi could be for Scotland what Nokia was for Finland's mobile communications industry. "We are, in my strong belief, at the same point here in Scotland," Prof Haas says. In the next 10 years we are setting out an industry that could have a huge impact. Li-Fi lowdown The basic idea behind LiFi is that visual light is a part of the electromagnetic spectrum that can be every bit as useful for transmitting information as radio waves, writes Mure Dickie. This is hardly a new concept - sailors have long communicated by flashing lights in Morse code, for example - but one given new applications by the introduction of LED lights, which can very precisely controlled. Communication can be between any two equipped devices, such as an underwater remotely operated vehicle and its control unit. In an office building a simple LED ceiling light fitting could be connected to a data network. PureVLC has patented techniques allowing high rates of data transmission using the very subtly flickering light to a receiver that could be sitting on a desk and linked to a PC, or possibly installed on a mobile device such as a tablet computer. If the light fitting also has a photodetector the communication can be two-way, otherwise the receiving device will need a separate network connection to send data back. Enthusiasts say use of light fittings will allow the rapid creation of huge numbers of separate data network cells, vastly increasing capacity.