  We investigate the practical network integration of differential phase shift
quantum key distribution following a cost-optimized deployment scheme where
complexity is off-loaded to a centralized location. User terminal equipment for
quantum state preparation at 1 GHz symbol rate is kept technologically lean
through use of a directly-modulated laser as optical encoder. Integration in a
passive optical network infrastructure is experimentally studied for legacy and
modern optical access standards. We analyze the implications that result from
Raman scattering arising from different spectral allocations of the classical
channels in the O-, S-, C- and L-band, and prove that the quantum channel can
co-exist with up to 19 classical channels of a fully-loaded modern access
standard. Secure-key generation at a rate of 5.1 times 10e-7 bits per pulse at
a quantum bit error ratio of 3.28 percent is obtained over a 13.5 km reach, 2
to 16 split passive network configuration. The high power difference of 93.8 dB
between launched classical and quantum signals in the lit access network leads
to a low penalty of 0.52 percent in terms of error ratio.
