  We demonstrate a quantum key distribution implementation over deployed dark
telecom fibers with polarisation-entangled photons generated at the O-band. One
of the photons in the pairs are propagated through 10km of deployed fiber while
the others are detected locally. Polarisation drifts experienced by the photons
propagating through the fibers are compensated with liquid crystal variable
retarders. This ensures continuous and stable QKD operation with an average
QBER of 6.4% and a final key rate of 109 bits/s.
