Adaptive optics for free-space communications

Free-space optical communications is traditionally used for point to point communications, and data rates of Gbit/s can be achieved over several km using this technique. We have developed a point to multipoint technique that allows transmission of information from a single station to a number of receivers. The transmitting station uses a microdisplay as a holographic element, which steers the light from the optical transmitter to the desired receiver. The element can be used to implement beam tracking, splitting (to allow multipoint transmission) and also to add phase to the transmitted wavefront, to track aberrations.