In telecommunications, Free Space Optics (FSO) is an optical communication technology that uses light propagating in free space to transmit data between two points. The technology is useful where the physical connections by the means of fibre optic cables are impractical due to high costs or other considerations.
Source: http://en.wikipedia.org/wiki/Free-space_optical_communication
Source: http://en.wikipedia.org/wiki/Free-space_optical_communication