Power efficient communication for high data-rate deep-space optical links

We demonstrate that quadrature phase-shift keying modulation with phase-sensitively pre-amplified coherent receivers provides the highest capacity for space- and deep-space optical communication links for transmission distances up to approximately Mars. It outperforms pulse-position modulation with photon counting detectors and surprisingly achieves better sensitivity than multi-dimensional and multi-format modulation formats with coherent detection. Our theoretical and numerical investigations are confirmed by experiments with an observed sensitivity as low as 0.8 photons per bit