  We demonstrate non-degenerate down-conversion at 810 and 1550 nm for
long-distance fiber based quantum communication using polarization entangled
photon pairs. Measurements of the two-photon visibility, without dark count
subtraction, have shown that the quantum correlations (raw visibility 89%)
allow secure quantum cryptography after 100 km of non-zero dispersion shifted
fiber using commercially available single photon detectors. In addition,
quantum state tomography has revealed little degradation of state negativity,
decreasing from 0.99 at the source to 0.93 after 100 km, indicating minimal
loss in fidelity during the transmission.
