Li-Fi is the great new marketing term for what has been known and referred to as VLC (visible light communication) for decades. It’s basically the same principle as communicating with ships by shuttering lanterns and using morse code.
Li-Fi is essentially communication using ultra-fast pulses of light and a photosensor. Any communication is essentially being able to send structured packets of data via binary pulses. Just like with dimming an LED, where you adjust the duty cycle, i.e. the ratio of on/off time of the rapid flashing of the light (see: pulse width modulation), there is a controller on the light which adjusts the rate and width of the pulses.
If a light is hooked up to an internet connection and has the required circuitry, it is possible to use the duration and frequency of these pulses to send encoded information, i.e. data, to a photoreceptor on, say, your laptop, where the computer will decode the light pulses into a data connection, and communicate back with its own pulses.
All of this is invisible to the naked eye due to either the frequencies being too fast to detect (see: flicker fusion rate), or they are dim. The benefits of Li-Fi include that there is much more available ‘spectrum’, whereas Wi-Fi is limited to a narrow band of rf. Li-Fi is also more secure than Wi-Fi due to the necessity of being in the environment to receive the data (light does not pass through walls), and it is also quite quick, ranging from gigabits for direct to 10s of megabits for indirect light exposure.
It’s quite the field at the moment! The tech is fascinating and forecast to explode in the next several years, but there are of course limitations. The first consumer products were demonstrated this year, but we don’t foresee you finding at your local store for another year.
Most interesting applications we’ve seen for Li-Fi are communications between cars (particularly self-driving) through headlights. As you can imagine, this makes sense because the line of sight is constrained, and the range can be superior in certain cases where you have objects going past each other and out of range at high speeds. This is made easier by the fact that LASER headlights seem to be the future, rather than LED.
For instance, the very quick rates used for Li-Fi (and even for fiber optic data transmission cables) have special hardware for blinking quickly.
In terms of the actual silicon itself, it’s in the nanoseconds ideally, but depends on the manufacturing, crystallinity, etc. Keep in mind that LEDs are at their core electrical devices. Also, if you add phosphor (like in white LEDs), then the time will be EXTRAORDINARILY lengthened by the fact that the phosphor is basically glow-in-the-dark goop that will slowly dim as it is ‘de-charged’.
Note : We are not sure if its primetime for Li-Fi yet. What we’re sure is that they’d find a way-out to get it worked as soon as possible for in the market!