Analysis of nonlinear polarization-mode dispersion in optical fibers with randomly varying birefringence

The set of equations describing the evolution of the electromagnetic field envelope in a nonlinear optical fiber with random birefringence are the Manakov-PMD equations with the variables: the electric field envelope measured relative to axes that follow the linear polarization state in the fiber, the group delay difference per unit length, and terms containing random coefficients driven by the random birefringence fluctuations. The first term on the right-hand side of the equation corresponds physically to the usual linear polarization-mode dispersion while the second term, referred to as nonlinear polarization-mode dispersion, is due to incomplete mixing of the nonlinearity on the Poincare sphere. We show that this term is unimportant for current communication systems but can become important for high-bit-rate time-division multiplexing systems approaching 100 Gbit/s