Design considerations for a Transportable Optical Ground Station with Adaptive Optics

IACTEC, as the technology transfer division of the Instituto de Astrofísica de Canarias (IAC), is initiating a program towards the practical applications of optical communications and specifically the quantum key distribution, taking advantage of its facilities and experience in free-space optical communications and its know-how in Adaptive Optics. The main objective of the optical communication group is related to the use of the atmospheric turbulence compensation to improve the performance of a Transportable Optical Ground Station (TOGS). This compensation is especially challenging when daytime operations are considered, and also if the TOGS is expected to work in virtually any location, including ordinary city buildings, where atmospheric turbulence is much worse than that found in astrophysical observatories. The role of Adaptive Optics could be especially relevant when using superconducting nanowires detectors, which can achieve very low dark counts when fed from a single mode fiber. In this situation, the ability to couple the light received at the telescope to the fiber is vital, and if the wavefront aberration caused by the atmospheric turbulence is corrected before the coupling to the fiber, the total loss of the quantum channel will be lowered and the key rate improved. This improvement will be estimated through simulations of the atmospheric turbulence characteristics of the different scenarios.