  We experimentally demonstrate multi-user distribution of polarization
entanglement using commercial tele- com wavelength division demultiplexers. The
entangled photon pairs are generated from a broadband source based on
spontaneous parametric down conversion in a periodically poled lithium niobate
crystal using a double path setup employing a Michelson interferometer and
active phase stabilisation. We test and compare demultiplexers based on various
technologies and analyze the effect of their characteristics, such as losses
and polarization dependence, on the quality of the distributed entanglement for
three channel pairs of each demultiplexer. In all cases, we obtain a Bell
inequality violation, whose value depends on the demultiplexer features. This
demonstrates that entanglement can be distributed to at least three user pairs
of a network from a single source. Additionally, we verify for the best
demultiplexer that the violation is maintained when the pairs are distributed
over a total channel attenuation corresponding to 20 km of optical fiber. These
tech- niques are therefore suitable for resource-efficient practical
implementations of entanglement-based quantum key distribution and other
quantum communication network applications.
