Correlated Photon-Pair Generation in a Highly Nonlinear Fiber Using   Spontaneous FWM
  We generate 1550 nm correlated photon pairs through the spontaneous four-wave mixing (SpFWM) process in a highly nonlinear fiber (HNLF). The pair source quality generation is evaluated by the coincidence-to-accidental ratio (CAR) parameter. It is verified that the spontaneous Raman scattering (SpRS) photons generated inside the fiber contribute to the degradation of the source. Nevertheless, a CAR value of 2.77 is found for a pump power at the input of the fiber of 1.1 mW. 
\'Alvaro J. Almeida, Lu\'is M. Martins, Nuno A. Silva, Nelson J. Muga,   and Armando N. Pinto
physics.optics