  We present a fiber-based source of polarization-entangled photon pairs that
is well suited for quantum communication applications in the 1.5$\mu$m band of
standard telecommunication fiber. Quantum-correlated signal and idler photon
pairs are produced when a nonlinear-fiber Sagnac interferometer is pumped in
the anomalous-dispersion region of the fiber. Recently, we have demonstrated
nonclassical properties of such photon pairs by using Geiger-mode InGaAs/InP
avalanche photodiodes. Polarization entanglement in the photon pairs can be
created by pumping the Sagnac interferometer with two orthogonally polarized
pulses. In this case the parametrically scattered signal-idler photons yield
biphoton interference with $>$90% visibility in coincidence detection, while no
interference is observed in direct detection of either the signal or the idler
photons.
