  By using an optical device based on the integration of a GRaded-INdex (GRIN)
rod lens and a single-mode optical fiber we efficiently collected photon pairs
generated by spontaneous parametric down-conversion. We show that this system
preserves the polarization entanglement of the 2-photon states. Hence this
device, characterized by a remarkable easiness of alignment and allowing for
high coupling efficiency of single-mode radiation, can be used with photons
entangled in various degrees of freedom, such as polarization and spatial
momentum, and to interconnect different sides of complex optical circuits.
