Depolarization in a single-mode optical fiber

The reduction of the degree of polarization of broad-band light due to propagation in ordinary single-mode fiber is examined theoretically and experimentally. Previous work is extended to account for polarization-mode coupling along the fiber by developing a model for one discrete mode-coupling center and extending it qualitatively to include multiple centers. The existence of nonzero degree of polarization in long lengths of fiber is shown to be due to mode coupling at particular positions along the fiber and the degree of polarization is shown to be related to the degree of coherence associated with the mode-coupling site. The experimental results generally support the model developed.