Nonlinear wave equation for wavelength/polarization multiplexed signals in fiber transmission

Abstract

Wavelength/polarization division multiplexing (WDM/PDM) schemes are standardly employed in trunk transmission systems, for which fiber nonlinearity is a serious problem. Generally, the signal transmission characteristics suffering from fiber nonlinearity have been analyzed using the nonlinear Schrödinger equation or the Manakov equation, which was originally presented for single-channel transmission. Therefore, when they are applied to WDM systems, the polarization states of each wavelength light are assumed to be identical, which is not fit to long-haul transmissions wherein the polarization states of WDM signals randomly and independently vary during the fiber transmission. Considering such conditions in WDM/PDM transmission systems, this paper presents a nonlinear wave equation for WDM/PDM signal transmission, which describes the signal behavior in systems where the polarization states of each WDM light are fully random and independent. A formula modified from the Manakov equation is derived using the polarization state coordinate of each signal light in WDM/PDM systems.