Analysis of the degree of polarization of optical waves in a single-mode optical fiber with random coupling

A single-mode optical fiber model is proposed with discrete mode-coupling centers having random coupling coefficients at regular intervals. The degree of polarization in a single-mode fiber with random-mode coupling does not approach zero with increasing fiber length. Numerical results show that the ensemble average of the degree of polarization approaches a nonzero value the magnitude of which depends on the coupling intensity, the light source spectrum, the fiber birefringence, and the spatial frequency of coupling centers, The theoretical and numerical results clarify the limitation of the perturbation iteration method for long optical fibers.