Nonlinear interaction of light propagation in a birefringentoptical fiber with external perturbations

Nonlinear interaction between two polarization modes by the optical Kerr effect is investigated when the light propagates in a birefringent optical fiber, with consideration of random external perturbations. A pair of nonlinear coupled differential equations are derived, which include both the linear birefringence fluctuation and the polarization mode coupling caused by the random external perturbations