Electronic Equalization of FBG Phase Ripple Distortions in 43 Gb/s WDM Systems

Within this paper we investigate in a first step the transmission performance for a 43-Gb/s wavelength division multiplex (WDM) system with channelized and broadband fiber Bragg gratings (FBGs) for dispersion compensation by statistical simulations. The results demonstrate the feasibility and limitations of replacing dispersion compensating fiber (DCF) in 43 Gb/s systems by FBGs and of upgrading a 10.7 Gb/s system with FBG dispersion compensation to 43 Gb/s. Phase ripple distortions and the narrow band filtering of the channelized FBG extend the OSNR requirements or lead to reduced possible transmission lengths. To overcome these limitations, linear feed-forward-equalizers (FFE), combinations of feed-forward and decision-feedback (FFE-DFE) equalizers, and nonlinear FFE-DFEs are introduced. We show that the OSNR penalty due to filtering and ripples can be significantly reduced by using nonlinear equalizers. Investigated modulation formats are NRZ-ASK (amplitude shift keying with non-return-to-zero pulse shape) and optical duobinary (ODB).