Optimum design for BB84 quantum key distribution in tree-type passive optical networks

We show that there is a trade-off between the useful key distribution bit rate and the total length of a deployed fiber in tree-type passive optical networks (PONs) for Bennet and Brassard 1984 protocol (BB84) quantum key distribution applications. A two stage splitting architecture where one splitting is carried in the central office and a second one in the outside plant and a figure of merit to account for the trade-off are proposed. We find that there is an optimum solution for the splitting ratios of both stages in cases of photon number splitting attacks and decoy state transmission. We then analyze the effects of the different relevant physical parameters of the PON on the optimum solution. (C) 2010 Optical Society of America