A 1.1km long all-fiber quantum key distribution experimental setup has been
realized for the first time at 850nm. The system employs the BB84 protocol
to establish a secret key between two parties, the security of which is gu
aranteed by Heisenberg's uncertainty relationship and the quantum nonclonin
g principle. Phase modulated single photons are used to carry the key. The
effective transmission rate is 3 bit/s, with a bit error rate of 9%.