Time-Domain Volterra-Based Digital Backpropagation for Coherent Optical Systems

• Published in: Journal of lightwave technology Vol. 33; no. 15; pp. 3170 - 3181
• Main Authors: Guiomar, Fernando Pedro, Batalha Amado, Sofia, Sanches Martins, Celestino, Nolasco Pinto, Armando
• Format: Journal Article
• Language: English
• Published: IEEE 01.08.2015
• Subjects: Approximation algorithms; Approximation methods; Coherent detection; Complexity theory; digital signal processing; Equalizers; Mathematical model; nonlinear equalization; Nonlinear optics; optical communication systems; Optical polarization; Volterra series; nonlinear equalization; Volterra series; optical communication systems; Coherent detection; digital signal processing
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2015.2435520

We propose a novel closed-form time-domain (TD) Volterra series nonlinear equalizer (VSNE) for the mitigation of Kerr-related distortions in polarization-multiplexed (PM) coherent optical transmission systems. The proposed TD-VSNE is obtained from the inverse Fourier analysis of a frequency-domain VSNE based on a frequency-flat approximation. Employing novel TD approximations, we demonstrate the equivalency between the VSNE algorithms formulated in time and frequency domains. In order to enhance the computational efficiency, we insert a power weighting time window in the TD-VSNE, yielding the weighted VSNE (W-VSNE) algorithm. We demonstrate that the convergence of the W-VSNE to its maximum performance is much faster than that of the TD-VSNE, thus requiring fewer parallel filters. Through numerical simulation of a 224-Gb/s PM-16QAM optical channel, we compare the performance/complexity tradeoff of the W-VSNE with the well-known split-step Fourier method (SSFM) and with the computationally optimized weighted SSFM (W-SSFM). Enabled by the use of fewer iterations and only two parallel W-VSNE filters, we demonstrate a reduction of up to ~45% on computational effort and ~70% on latency, in comparison with the W-SSFM.