Analytical Treatment of Randomly Birefringent Periodically Spun Fibers

Abstract—Spun fibers are increasingly used in telecommunica-tion systems because their polarization-mode dispersion (PMD) is lower than that in unspun fibers. In this paper, we investigate the ef-fects of a periodic spin on the PMD of fibers with randomly varying birefringence. Numerical simulations show that when the spin pe-riod is of the same order as or larger than the beat length, the mean differential group delay of a spun fiber depends on the model used for the random birefringence. We then carry out a general theo-retical analysis using the second Wai–Menyuk model, which is the only model of fiber birefringence to date that is consistent with polarization optical time domain reflectometry data. Finally, we consider some particular regimes by means of a perturbative ap-proach. Index Terms—Beat length, birefringence correlation length, dif-ferential group delay, fiber birefringence, polarization-mode dis-persion (PMD), spun fibers. I