Field test demonstration of Adaptive Optics pre-correction for a Terabit Optical Communication Feeder Link

A 10 km ground-to-ground field test of a Terabit/s Optical Feeder Link demonstrator has been carried out. The demonstrator aimed for end-to-end communication performance with the use of Adaptive Optics pre-correction to mitigate the atmospheric turbulence disturbances of the FSO channel. It further includes the multiplexing of multiple uplink channels and RF end-to-end modems to prove the technical feasibility of supporting a Terabit/s communication link. The field test - performed in July 2022 - demonstrates error free communication for over 10 minutes. This achievement proves the feasibility of a digital transparent communication architecture for the Terabit/s Feeder link application. The field test results are presented jointly with a companion paper [1] which focusses on the communication aspects. The Adaptive Optics (AO) pre-correction performance is analyzed against the atmospheric turbulence strength and the number of corrected AO modes. The encountered turbulence conditions during the field test caused irradiance fluctuations in the strong fluctuation regime. The field test results show a significant AO wavefront error correction on the downlink. For the uplink irradiance levels, a modest advantage of pre-correcting higher wavefront modes is found against the pre-correction of only the tip-tilt modes. Finally, with respect to the uplink fading characteristics, the AO pre-correction leads to a reduction of the mean-fade time of approximately 20-30%, compared to AO tip-tilt pre-correction only.