High-Purity Telecom-Band Entangled Photon-Pairs via Four-Wave Mixing in   Dispersion-Shifted Fiber
  We have studied the purity of entangled photon-pairs generated in a dispersion-shifted fiber at various temperatures. Two-photon interference with visibility > 98% is observed at 77K, without subtraction of the background Raman photons. 
K. F. Lee, J. Chen, C. Liang, X. Li, P. L. Voss, and P. Kumar