  We report on a two-photon interference experiment in a quantum relay
configuration using two picosecond regime PPLN waveguide based sources emitting
paired photons at 1550 nm. The results show that the picosecond regime
associated with a guided-wave scheme should have important repercussions for
quantum relay implementations in real conditions, essential for improving both
the working distance and the efficiency of quantum cryptography and networking
systems. In contrast to already reported regimes, namely femtosecond and CW, it
allows achieving a 99% net visibility two-photon interference while maintaining
a high effective photon pair rate using only standard telecom components and
detectors.
