50 Mbps optical homodyne communication receiver with a photorefractive optical beam combiner

Performance measurements are reported for a coherent homodyne optical communication receiver that contained an iron-doped indium phosphide photorefractive beam combiner, rather than a conventional optical beam splitter. The system attained a bit error probability of 10/sup -6/ at received signal powers corresponding to about 75 detected photons per bit. No precision beam alignment or mode-matching optics were required, and tracking of slow phase changes between signal and local-oscillator light was performed automatically by the dynamic nature of the photorefractively formed refractive-index grating. The system used phase-modulated Nd:YAG laser light at lambda =1.06 mu m.<>