Fig. 2: Topographical situation of the 53 km turbulent free-space optical (FSO) link.
From: Tbit/s line-rate satellite feeder links enabled by coherent modulation and full-adaptive optics

a Aerial view of the FSO transmission experiment with b the corresponding elevation profile. (swiss map data: edited from Federal Office for Topography swisstopo. Europe map data: edited from Natural Earth)