Reducing Computational Complexity of Neural Networks in Optical Channel Equalization: From Concepts to Implementation

Pedro J. Freire, Antonio Napoli, Diego Arguello Ron, Bernhard Spinnler, Michael Anderson, Wolfgang Schairer, Thomas Bex, Nelson Costa, Sergei K. Turitsyn, Jaroslaw E. Prilepsky

Research output: Contribution to journalArticlepeer-review


This paper introduces a novel methodology for developing low-complexity neural network (NN) based equalizers to address impairments in high-speed coherent optical transmission systems. We present a comprehensive exploration and comparison of deep model compression techniques applied to feed-forward and recurrent NN designs, assessing their impact on equalizer performance. Our investigation encompasses quantization, weight clustering, pruning, and other cutting-edge compression strategies. We propose and evaluate a Bayesian optimization-assisted compression approach that optimizes hyperparameters to simultaneously enhance performance and reduce complexity. Additionally, we introduce four distinct metrics (RMpS, BoP, NABS, and NLGs) to quantify computing complexity in various compression algorithms. These metrics serve as benchmarks for evaluating the relative effectiveness of NN equalizers when compression approaches are employed. The analysis is completed by evaluating the trade-off between compression complexity and performance using simulated and experimental data. By employing optimal compression techniques, we demonstrate the feasibility of designing a simplified NN-based equalizer surpassing the performance of conventional digital back-propagation (DBP) equalizers with only one step per span. This is achieved by reducing the number of multipliers through weighted clustering and pruning algorithms. Furthermore, we highlight that an NN-based equalizer can achieve better performance than the full electronic chromatic dispersion compensation block while maintaining a similar level of complexity. In conclusion, we outline remaining challenges, unanswered questions, and potential avenues for future research in this field.

Original languageEnglish
Pages (from-to)4557-4581
JournalJournal of Lightwave Technology
Issue number14
Early online date5 Jan 2023
Publication statusPublished - 15 Jul 2023

Bibliographical note

This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see

Funding: This paper was supported by the EU Horizon 2020 program under the
Marie Sklodowska-Curie grant agreements 813144 (REAL-NET) and 860360
(POST-DIGITAL). JEP is supported by Leverhulme Trust, Grant No. RP-
2018-063. SKT acknowledges support of the EPSRC project TRANSNET.


  • Artificial neural networks
  • Bayesian Optimizer
  • Coherent Detection
  • Computational Complexity
  • Computational modeling
  • Equalizers
  • Fiber nonlinear optics
  • Neural Network
  • Nonlinear Equalizer
  • Nonlinear optics
  • Optical fibers
  • Pruning
  • Quantization
  • Symbols


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