High-bandwidth coherent optical communication over 10.3  km of turbulent air.

We demonstrate 111.8 Gb/s coherent optical communication throughput over a 10.3 km folded free-space laser range. Folded links are low complexity to establish and provide a high uptime for testing equipment. The communication signals were sourced from an un-modified commercial off-the-shelf transceiver intended for long-haul fiber networks. Wavelength dependence was explored by testing 52 optical C-band channels over the course of an evening. In the future, such high-bandwidth communications will be used in feeder links from satellites in geosynchronous orbit. Optical power measurements of the received signal are compared with atmospheric theory to determine the turbulence strength exhibited and therefore the applicability of the laser range to space-to-ground links. We show that the high-uptime, 10.3 km laser range is suitable for testing high-bandwidth space-to-ground optical communication systems intended for links to geosynchronous orbit at 20°-50° elevation.