Nonlinear phase nonreciprocity in a ring fiber interferometer

An analysis is made of the propagation of radiation in a single-mode optical fiber which does not conserve the wave polarization state. It is shown that nonlinear properties of the fiber may give rise to nonreciprocal phase shifts between the opposite waves in a ring fiber interferometer. General relationships are derived for a fiber with accidental birefringence and the nonreciprocity is estimated.