Photon-counting 1.55 μm optical communications with pulse-position modulation and a multimode upconversion single-photon receiver

We report single-photon frequency upconversion of multimode light from 1.55 to 0.532 mum and demonstrate an end-to-end optical link that emulates photon-starved communications and atmospheric propagation. Using 64-ary PPM and a 1/2-rate serially concatenated turbo code we achieve a decoded efficiency of 0.3 detected photons/bit.