Research and development of free-space laser communications and quantum key distribution technologies at NICT

Since 2006, ground-to-satellite laser communication experiments have been successfully performed using intensity modulation/direct detection (IMDD) between the National Institute of Information and Communications Technology (NICT) optical ground station located in Tokyo and a low earth orbit (LEO) satellite. With the advent of coherent binary phase-shift keying (BPSK) receivers in orbit by a German satellite, it is now absolutely imperative to establish interoperability between the different optical communications systems. At NICT, an optical receiver that can demodulate both IMDD and coherent optical signals for free-space laser communications has been developed that can recover the carrier phase after homodyne detection by means of digital signal processing (DSP). A transportable optical ground station has also been developed for site-diversity purposes in order to increase accessibility between terrestrial and space systems. A new NICT mid-term research plan has started since April 2011 and this paper presents research and development in free-space laser communications technologies at NICT.