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This paper focuses on optical links from ground to a geostationary satellite, using adaptive optics to pre-compensate the wave-front of the uplink beam. We present the numerical prediction of the irradiance statistics at the satellite. Uplink beam diameters, as well as the turbulence strength in the boundary layer and in the tropopause are varied. Results show, that the choice of uplink beam diameter significantly affects the fading statistics, in particular the shape of the probability density function. In a realistic worst case (30° elevation, day-time turbulence, sea level), the optimum beam diameter, showing minimum irradiance fluctuation at the target, is around 20 cm. In that case, the probability of fades larger than 6 dB (with respect to the diffraction limit) is approx. 10 -3 .A breadboard of such a closed-loop adaptive-optics pre-compensation system has been implemented. It comprises a Shack-Hartmann wavefront sensor, two tip/tilt mirrors, a 140-element deformable mirror, a far-field propagation simulator, and two rotating turbulence phase screens (simulating tropopause and atmospheric boundary layer, respectively). The link geometry is representative of the intended application in an optical feeder link for geo-stationary satellites. Preliminary test results confirm the numerical predictions.

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Contraves Space AG is currently developing the OPTEL family of optical terminals for free-space optical communications. The optical terminals within the OPTEL family have been designed so as to be able to position Contraves Space for future opportunities open to this technology. These opportunities range from commercial optical satellite crosslinks between geostationary (GEO) satellites, deep space optical links between planetary probes and the Earth, as well as optical links between airborne platforms (either between the airborne platforms or between a platform and GEO satellite). This paper will present an overview of the space based and airborne system architectures that the Contraves Space family of OPTEL terminals have been designed to support, provide a description and performance summary of each OPTEL terminal and the key technologies that have been developed.