  We present a quantum key distribution (QKD) system based on polarisation
entanglement for use in telecom fibers. A QKD exchange up to 50km was
demonstrated in the laboratory with a secure key rate of 550 bit/s. The system
is compact, portable with a fully automated start-up and stabilisation modules
for polarisation, synchronisation and photon coupling allow a hands-off
operation. Stable and reliable key exchange in a deployed optical fiber of 16km
length was demonstrated. In this fiber network we achieved over two weeks an
automatic key generation with an average key rate of 2000 bit/s without manual
intervention. During this period, the system had an average entanglement
visibility of 93%, highlighting the technical level and stability achieved for
entanglement-based quantum cryptography.
