Improvements in and relating to free-space optical communications

A multi-aperture free-space optical communications receiver 1 comprises a plurality of telescopes 2, each having a clear objective aperture 7 with a diameter between 50mm and 250mm. Each telescope is arranged in association with a respective wavefront detector and a steerable reflector unit 9, including a deformable mirror controlled by the wavefront detector. The deformable mirror corrects for a non-flat wavefront 12. The steerable reflector steers light from the telescope into an optical fibre 14, which is connected to a respective optical receiver 3. A coherent combiner unit 4 is configured to coherently combine the signals from each optical detector. The deformable mirror is preferably a zonal bimorph deformable mirror (ZBDM) and the wavefront detector is preferably a Shack-Harmann wavefront sensor. Each deformable mirror may have a plurality of apertures in its reflective surface, each in optical communication with the wavefront detector. At least one of the optical receivers may share its telescope with a transmitter. The steerable reflector may have a tilting or/and tipping function. The invention may be applied in optical satellite communication ground stations.