FLICKERING lamps are normally a headache-inducing nuisance. But if the flickering happens millions of times a second—far faster than the eye can see or the brain respond to—then it might be harnessed to do something useful, like transmitting data. That, at least, is the idea behind a technology dubbed Li-Fi by its creators.
Li-Fi works with light-emitting diodes (LEDs), an increasingly popular way of illuminating homes and offices, and applies the same principle as that used by naval signal lamps. In other words, it encodes messages in flashes of light. It can be used to create a local-area network, or LAN, in a way similar to the LANs made possible by standard, microwave-based Wi-Fi.
Such LANs would, Li-Fi’s supporters believe, have two advantages over standard Wi-Fi. One is that light does not penetrate walls. A Li-Fi LAN in a windowless room is thus more secure than one using Wi-Fi, whose microwave signals pass easily through most building materials and can thus be listened to by outsiders. The other advantage is that light does not interfere with radio or radar signals in the way that microwaves sometimes do. Li-Fi can therefore be installed in hospitals, nuclear plants and other sites where Wi-Fi might create dangerous interference with electronic kit.
One business about to benefit from this selectivity is commercial aviation. Though aircraft avionics have been hardened over the years, to reduce the risk of interference from radio and microwave signals, using Li-Fi would make absolutely certain. It would mean that LANs could be set up in the cabin, distributing entertainment to passengers and permitting those with Li-Fi-equipped phones and computers to contact the outside world.
This arrangement would also save on weight, as passenger-entertainment systems would no longer have to be fed by cables. To this end Airbus, a big European aircraft-maker, let Velmenni, an Indian firm, spend six months earlier this year installing and testing a Li-Fi network in a mocked-up passenger cabin of one of its planes. Velmenni hopes to use passengers’ reading lights to broadcast the signal. Luciom, a French firm, is even further advanced. In January 2017 it will begin installing Li-Fi on passenger jets built either by Airbus or by its American rival, Boeing (a non-disclosure agreement forbids it from saying which one).
In the longer run, though, it is buildings that Li-Fi’s manufacturers have their eyes on. PureLiFi, a British firm that sells components to lighting manufacturers, plans to use the same cable to carry power and data to the LEDs themselves. That should make the system simple to install. PureLiFi is also designing LEDs that radiate data even when dimmed, so that a film can be streamed into a room and shown with the lights down.
Installing a Li-Fi LAN, then, should not be too difficult. But for the technology to succeed, computers, phones and other signal-receiving devices will also have to be modified, so that they can pick up and reply to optical transmissions. To give that capability to existing kit engineers at Luciom have made a dongle that plugs into a standard USB port. This dongle contains both an ordinary LED (though it is one that emits infra-red flashes, which are invisible to the human eye) to send data to the LAN, and the opposite of an LED—a photodiode that converts light into electricity rather than the other way around—to receive data.
PureLiFi, looking further ahead to a time when Li-Fi has become routine, is miniaturising such components with the intention of embedding them into devices at the point of manufacture. Nor is it alone in this desire. Zero.1, based in Dubai, says it has managed to tweak the cameras in the latest smartphones to run Li-Fi. Perhaps more pertinently, the intentions of Apple, the world’s most valuable listed company, were revealed earlier this year when it emerged that the term “LiFiCapability” is buried in the code of the iOS 9.1 operating system used by one of its most successful products, the iPhone.
Li-Fi may spread outdoors, too. Sunlight spoils its signals during the daytime, but in the hours of darkness Li-Fi-enabled streetlamps should work perfectly well. Gabe Klein, an entrepreneur who was once the boss of Chicago’s transport department, says the city has begun testing the idea of adding Li-Fi to the LED-based street lighting now being installed there. One potential beneficiary of this idea, if it succeeds and spreads, is Trópico, a Brazilian streetlamp-maker. According to Daniel Auad, Trópico’s owner, the Li-Fi-enabled streetlamps the firm is now working on should sell for about $325 a piece—a premium of only $75 over the non-enabled variety.
The technology may even be co-opted as a navigation tool in places, such as many buildings, that signals from the satellite-based global-positioning system cannot reliably penetrate. In this case the flickering LEDs act not as message-carriers but as beacons, permitting suitably equipped devices to locate themselves. Luciom has already installed such beacons in the ceiling lights of Orly airport, near Paris, and in a hypermarket in Lille. In Orly, the beacons (which are currently under test and used only by employees) will eventually show passengers to, for instance, the correct baggage carousel for their flight. In the hypermarket they direct shoppers with a Luciom dongle on their smartphones to the locations of desired items.
Li-Fi, then, seems to be developing as a useful addition to the list of ways electronic devices can communicate. That it will actually replace conventional Wi-Fi seems unlikely. But by extending the amount of spectrum available for communications it may, as it were, lighten the load.