The infrared light is used for many years for the communication directly between nearby devices to each other, such as remote control and your television, for example.
These waves are not able to cross barriers and the signal strength is dissipates rapidly reach is low. In short, the flow may, however, be quite high: IrDA organization has developed a series of standards, the most Quick to date, the Very Fast Infrared (VFIR) achieves a throughput of 16 Mb/s. It is therefore perfectly suited for data exchange between two terminals, eg for exchanging business cards between two smartphones, or copy pictures from a digital camera to a computer. The directionality and the low signal range provide some security against hackers tapping. Infrared waves absolutely not interfere with waves radio which is significant in an electromagnetic environment “noisy”.
Infrared is often better suited than WiFi to make WPAN, it can UA say, as we have seen, to allow exchanges between devices located near each other. Note that the IrDA standards also allow achieve real WLAN, but their interest is very limited compared to WiFi for this use.
Point to point
By concentrating the signal in a coherent beam, very narrow, with the aid of laser diodes rather than mere Light-Emitting Diodes (LED), it is possible to make links point to point several miles, but in practice it is better to be limited a few blocks away, otherwise the rain and fog will cut frequently the connection.
Here again the directional aspect of the laser and the fact that it does not interfere with the radio are advantages over WiFi to set up a point to point link Urban saturated airwaves.