  We demonstrate a novel polarization-entangled photon-pair source based on
standard birefringent polarization-maintaining optical fiber. The source
consists of two stretches of fiber spliced together with perpendicular
polarization axes, and has the potential to be fully fiber-based, with all bulk
optics replaced with in-fiber equivalents. By modelling the temporal walk-off
in the fibers, we implement compensation necessary for the photon creation
processes in the two stretches of fiber to be indistinguishable. Our source
subsequently produces a high quality entangled state having (92.2 \pm 0.2) %
fidelity with a maximally entangled Bell state.
