Integrating a QPSK Quantum Key Distribution Link
  We present the integration of the optical and electronic subsystems of a BB84-QKD fiber link. A highspeed FPGA MODEM generates the random QPSK sequences for a fiber-optic delayed self-homodyne scheme using APD detectors. 
M. B. Costa e Silva, Q. Xu, S. Agnolini, S. Guilley, J-L. Danger, P.   Gallion, F. J. Mendieta