I. Introduction
Parametric devices based on four-wave mixing (FWM) in fibers can amplify, frequency convert, phase conjugate, regenerate, and sample optical signals in classical communication systems [1]–[4]. However, because transmission fibers do not preserve the signal polarizations, these devices must operate in signal-polarization independent manners. Parametric devices can also generate photon pairs for quantum communication experiments [5]–[8]. Some experiments require polarized photons, whereas others require polarization-entangled photons. For both types of application, the polarization properties of FWM are important.