Silica fibers as spontaneous four-wave mixing sources of photon pairs: Raman noise revisited

Sources of photon pairs based on spontaneous four-wave mixing in silica fibers are generally considered limited by the spectrally broad spontaneous Raman scattering noise. I experimentally show that fluorescence from native or residual doping defects in silica fibers can become preponderant in situations where Raman scattering is normally eliminated, revealing a new, to the best of my knowledge, source of noise in silica-fiber-based sources of pairs of photons. I show that this noise depends on the fiber used, and that a new parameter must be carefully surveyed for the optimization of a fibered source of entangled pairs of photons.