LiFi: A Visible Technology


Today, LED sources to tend to dominate urban landscapes. Their implementation also paves the way for new information Technology: the LiFi. With it, lighting would become a real vector of data, both indoors and outdoors.

Communicate with the light around us This is the idea of LiFi technology (Light Fidelity), named in 2011 and whose first devices date back to the late 2000s. This wireless technology relies on visible light to transmit information. Its application seems all the more simple as the so-called visible light sources flood today the streets of our cities. Reliable and inexpensive, the LEDs (Light Emitting Diode) are a perfect example. LiFi is directly inspired by advances and know-how developed primarily for fiber optic telecommunications. However, the differences are numerous: the infrared gives way to visible wavelengths (380 – 780 nm); the signal propagation medium is no longer guided as for the optical fiber but through the air itself; not to mention that the lighting and the information take place simultaneously. LiFi thus appears to be a good complement to radio frequency-based technologies that can not interfere with their wavelengths.

Advantages and Disadvantages of LiFi

One of the major advantages of LiFi technology lies in its very high potential throughput. While Wi-Fi reaches average speeds of 50 Mb / s, LiFi research groups have managed to achieve speeds of over 4 Gb / s – 80 times more than for Wi-Fi. , the impact of radio frequencies on health is still questionable, and some places are totally lacking – hospitals and aircraft for example. LEDs and their long life – about 10,000 hours against 100 for an incandescent bulb – could, therefore, allow the LiFi to invite in our cities, and more.

However, health risks due to LEDs do exist. Their spectrum that stings in the blue seems to harm both our eyes and our sleep. Another drawback related to LEDs, their field of vision must remain empty between the transmitter and the receiver when Wi-Fi ignores obstacles while diffusing in all directions. As a result, the LiFi is sensitive to signal interruptions, even though its restricted field of vision promises increased privacy. Finally, the LiFi is based on the principle of modulation of light, and therefore of light power variations. These variations can be perceived by the human eye. The observer is then confronted with a flickering effect more or less marked, and more or less pleasant.

Perspectives Rooted in the future

Whether indoor or outdoor, the LiFi suggests many applications. Indoors first. The visitor of a museum could locate in the labyrinth of the corridors with the help of the allowed by the lamp under which it would be held. A case was unique to imposing and complex buildings. Keeping the example of the museum, the LED illuminating a work would be able to display various additional information for visitors in audiovisual or video format. The Internet provided by Bluetooth, Wi-Fi or even by wire would be complemented by a light component LiFi. In terms of outdoor operation, the challenges are many – weather conditions (night, day, full sun, rain, …) being just one example.

Nevertheless, this technology could interest the environment of the autonomous car. Thus, the vehicle-vehicle communication would be via LED headlights, also useful to exchange with road signs. Again, the obstacles to overcome are numerous, especially in terms of possible configurations: crossings, turns, urban areas, etc. But the future also belongs to organic transmitters and receivers – OLED (Organic LED) for transmitters, OPV (Organic Photovoltaic) and OPD (Organic Photo detector) for receivers. These components, flexible and very thin, have the advantage of eventually transforming any surface transmitter or receiver potential. Possibilities that leave you thinking even if, for the moment, the receivers are still added and bulky modules.

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