Antialiased Transmitter-Side Digital Backpropagation

Abstract

Digital backpropagation (DBP) is an electronic scheme for compensating nonlinear distortions in fiber transmission systems. Due to the nonlinearity-induced spectral broadening, the data must be oversampled to avoid aliasing, which increases the complexity and power consumption of the scheme. In this work, we show that aliasing can alternatively be prevented by distributed antialiasing filters, at a lower complexity. We proposed a new modified split-step Fourier method (SSFM) with easy-to-implement low-pass filters (LPFs) in the linear steps to avoid aliasing due to spectral broadening. Both the forward fiber propagation and a transmitter-side DBP are simulated using the modified SSFM. High-order modulation formats such as 256-ary quadrature-amplitude-modulation (256-QAM) and 1024-QAM transmissions at 28 Gbaud and 64 Gbaud over 1000 km fiber are considered, and our results show that the complexity of the DBP can be reduced by up to 50%. The optimal bandwidth of the LPFs is studied for both forward propagation and the DBP.