It occurs in the expressions permittivity of free space and permeability of free space; one defines the permittivity or permeability of a given material. In this setting it simply means no material present, and so corresponds to a theoretical idea of measurement carried out on a perfect vacuum.
FreeSpace Optics (FSO) or Optical Wireless, refers to the transmission of modulated visible or infrared (IR) beams through the air to obtain optical communications.
Historically, FreeSpace Optics (FSO) or optical wireless communications was first demonstrated by Alexander Graham Bell in the late nineteenth century (prior to his demonstration of the telephone!).
Unlike radio and microwave systems, FreeSpace Optics (FSO) is an optical technology and no spectrum licensing or frequency coordination with other users is required, interference from or to other systems or equipment is not a concern, and the point-to-point laser signal is extremely difficult to intercept, and therefore secure.
ORBITER is a free flight simulator that goes beyond the confines of Earth's atmosphere.
Launch the Space Shuttle from Kennedy Space Center to deploy a satellite, rendezvous with the International Space Station or take the futuristic Delta-glider for a tour through the solar system - the choice is yours.
Planetary motion, gravitation effects, freespace and atmospheric flight are accurately modelled.
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