Oh yes, and there are free space optical units as well - "laser" if you like. Can go long distances at high speed (if you are prepared to pay for the better units) - but do need clear LOS and can be a right PITA to set up as the beamwidth is very narrow.
We had one for another customer (180m span), and from graphing the signal strength we could make out the movement due to thermal expansion of the buildings in good sunlight !
We had one for another customer (180m span), and from graphing the signal strength we could make out the movement due to thermal expansion of the buildings in good sunlight !