|
For the next generation of very high throughput communication satellites, free-space optical (FSO) communication between ground stations and geostationary telecommunication satellites is a potential solution to overcome the limitations of RF links. To mitigate atmospheric turbulence effects, TNO proposes Adaptive Optics (AO) to apply uplink pre-correction. As a successor of Optics Feeder Link Adaptive Optics (OFELIA) breadboard [1], [2], the Terabit Optical Communication Adaptive Terminal (TOmCAT) project phase 2 aims to demonstrate the AO pre-correction technology for a terabit Optical Ground Station (OGT) in a ground-to-ground link field test over 10 km. Within this demonstrator an upgraded version of the OFELIA breadboard is used as optical bench for the AO (pre-)correction, but moreover the demonstrator enables the (future) integration of equipment for the final OGT configuration including the Beam Multiplexer (BMUX) and communication equipment. Apart from the OGT demonstrator, the overall layout of the field test has been upgraded, including the test site and the Ground Support Equipment (GSE), with the goal to create a better understanding of the encountered link phenomena and the instant (turbulence) conditions at which it was measured. New additions to the GSE are several weather stations placed along the link path to quantify the local turbulence and to relate the measured link performance to the instant turbulence conditions. The test campaign is split in two successive field tests: First the AO Demonstrator evaluates the upgraded AO pre-correction performance with a single non-modulated link, followed by the OGT Demonstrator which will include the multiplexing of multiple uplink channels and RF end-to-end modems to prove the technical feasibility of supporting a terabit communication link. This paper covers the design of the AO demonstrator and GSE, the field test layout and the preliminary results for the AO demonstrator field test. For the downlink correction the residual Wave Front Error (WFE) is presented. The pre-correction performance is depicted in the uplink transmission loss and scintillation, all as function of the encountered turbulence conditions.
|
