A Compact Receiver Module For Satellite-Ground QKD

The low-cost small aperture commercial optical ground stations (OGSs) will play an important role in the realization of a global scalc satellite-to-ground quantum key distribution (QKD) networks. OGSs with < 60 cm diameter tclcscope and a small mount, can have stringent size and weight limits on the pay load that can be accommodated. In order to ensure easy integration with an OGS, we have designed and produced a 40 x 30 x 10 cm receiver module which comprises polarization detection optics, fine point and track (PAT) subsystem and coarse wavelength division multiplexing optics for receiving optical signals over the visible, near-infrared and infrared spectrum. The tracking capability of the module to track multiple beams of different wavelength is evaluated in an emulated beam-wander induced free-space link. The receiver module is characterized for transmission loss and polarization extinction ratio (PER) by sending an 844 nm collimated beam to the module in a 3 m free-space link and measuring the power coupled into the four single mode fibers (SMF) for H, V, D and A polarized components. Furthermore, we have used the receiver module in our satellite-to-ground QKD emulator and have measured the secure key that can be generated within different maximum elevation satellite overpasses when the quantum signal is coupled into AR-coated SMF. Such modules can be incorporated into optical ground stations (OGS) to mitigate atmospheric beam-wandering and coarse misalignment while allowing wavelength division multiplexing of multiple visible, near-infrared and infrared beams to enable co-propagation of classical and quantum communication beams for real-time QKD.