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We report on the construction of polarization-entangled photon sources for quantum key distribution (QKD) testbed using nonlinear optical process of spontaneous parametric down-conversion (SPDC) pumped by a 266-nm and 351-nm continuous wave (cw) and a 415-nm femtosecond-pulsed laser sources. The eÆcient coupling of down-converted photons at 702 nm and 830 nm into optical single-mode ber has enabled us to increase the rate of entangled-photon pairs available for transmission over communication channels with a high degree of polarization entanglement. The detection and characterization of the entangled-photon-state properties has been performed using commercially available Silicon avalanche photodiodes (APD) as well as using a novel photon-number-resolving cryogenic photodetector, which has been developed by our colleagues at the Boulder Division of NIST and brought to BU for tests with elements of the future DARPA Quantum Network