Visible light technology consists of using visible light spectrum as a mean to transfer data, as opposed to the Wi-Fi waves that belong to the radio spectrum. In other words, we can use our already existing lightning system as wireless data transmitters as an alternative to the Wi-Fi technology, with its expensive, capacity limited and unsecured modems. The Light-Fidelity (Li-Fi, versus Wireless-Fidelity for Wi-Fi) is made possible with LED light bulbs whose light amplitude pulses at the incredibly high frequencies that the visible light spectrum offers (430-770THz). These pulses are completely invisible to the human eye, yet it allows to transmit data, at speeds more than a hundred times higher than the fastest internet transmission, using conventional Wi-Fi.
The concept was firstly introduced in a TED conference by Harald Haas (University of Edinburgh) in 2011, and has inspired many companies (PureLiFi in 2014, Philips Signify LiFi systems in 2018) since then. Li-Fi only requires to change light bulbs to Li-Fi LED bulbs (having a transmitter-receiver chip), and connect the same transmitter-receiver component to our devices. For computers, USB sticks already exists, but it can of course be integrated to any electronic tool to which we want to provide a wireless and powerful connection. The light does not have to be bright to transmit; it be toned down low enough so the human eye does not perceive light anymore but the receiver still does. Additionally, the LED emitted light will not suffer from the regular conventional light that already exists; the latter is a continuous signal, whereas Li-Fi waves are oscillating waves at very high frequency, and receivers are only sensitive to the fast variations of the light intensity (it is precisely where all the transmitted data is contained).
The advantages of the Li-Fi technology are natural consequences of its inherent nature (just using visible light to transmit data) and are the following: the visible light spectrum is ten thousand times larger than the radio frequency spectrum. This means there are ten thousand times more available capacity, and much higher transmission speeds*. The Li-Fi technology is inccredibly efficient and cheap, since lights are everywhere, already functioning and widely used. It is also available in all RF hostile environments such as airplanes, hospitals, gas stations, and even RF-isolated areas such as lifts and undergrounds. One massive strength of the Li-Fi is certainly the security aspect: since all the data stream is contained in a light beam, anyone nor anything can hack or access it outside the room where the communication takes place, because light does not travel through walls. Hence, governemental institutions and high security facilities can protect their data transmissions effortlessly. Finally, the Li-Fi is the surest way to reach an Internet of Things configuration, since light covers all electronical devices to be connected together (mobile phone, fridge, window shut, television, speakers, cameras,...). Visible light communication is already used in some applications, and Philips Lightning (now called Signify) has started to put Li-Fi lamps on the market in 2018.