Visible light communication (VLC) is a data communications medium
using visible light between 400 THz (780 nm) and 800 THz (375 nm).
Visible light is not injurious to vision.
The technology uses fluorescent lamps
(ordinary lamps, not special communications devices)
to transmit signals at 10 kbit/s,
or LEDs for up to 500 Mbit/s.
Wiki http://en.wikipedia.org/wiki/Visible_light_communication