Very basically radar is about using short wave radio waves often microwaves, to get information about how external things are moving in space or the air. It relies on the idea of a reflected signal.
A simple radar system tracking an object.
Optical fibre communications is about using much shorter wavelengths, often visble light, in the nanometre range for transferring huge volumes of information. Usually it is between static objects like computers. The medium is a special kind of glass or plastic and relies on total internal reflection.
fibre optic communication. Note that the beam is contained. In radar the beam is not contained.
The only significant similariy is that both use electromagnetic radiation to move information about.
References sources:
- http://en.wikipedia.org/wiki/Radar
- http://en.wikipedia.org/wiki/Optical_fibre