Blind nonlinearity equalization by machine learning based clustering for single- and multi-channel coherent optical OFDM

Elias Giacoumidis, Amir Matin, Jinlong Wei, Nick J. Doran, Liam P. Barry, Xu Wang

Research output: Contribution to journalArticlepeer-review


Fiber-induced intra- and inter-channel nonlinearities are experimentally tackled using blind nonlinear equalization (NLE) by unsupervised machine learning based clustering (MLC) in ∼46-Gb/s single-channel and ∼20-Gb/s (middle-channel) multi-channel coherent multi-carrier signals (OFDM-based). To that end we introduce, for the first time, Hierarchical and Fuzzy-Logic C-means (FLC) based clustering in optical communications. It is shown that among the two proposed MLC algorithms, FLC reveals the highest performance at optimum launched optical powers (LOPs), while at very high LOPs Hierarchical can compensate more effectively nonlinearities only for low-level modulation formats. FLC also outperforms K-means, Fast-Newton support vector machines, supervised artificial neural networks and a NLE with deterministic Volterra analysis, when employing BPSK and QPSK. In particular, for the middle channel of a QPSK WDM coherent optical OFDM system at optimum -5 dBm of LOP and 3200 km of transmission, FLC outperforms Volterra-NLE by 2.5 dB in Q-factor. However, for a 16-quadrature amplitude modulated single-channel system at 2000 km, the performance benefit of FLC over IVSTF reduces to ∼0.4 dB at a LOP of 2 dBm (optimum). Even when using novel sophisticated clustering designs in 16 clusters, no more than additional ∼0.3 dB Q-factor enhancement is observed. Finally, in contrast to the deterministic Volterra-NLE, MLC algorithms can partially tackle the stochastic parametric noise amplification.
Original languageEnglish
Pages (from-to)721-727
JournalJournal of Lightwave Technology
Issue number3
Early online date1 Dec 2017
Publication statusPublished - 24 Feb 2018

Bibliographical note

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

Funding: Partnership Resource Project of Quantum Communications Hub (EPSRC), EU Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 713567, SFI CONNECT Research Centre and Sterlite Techn. Ltd. We thank S. T. Le (Nokia-Bells labs) and M. E. McCarthy (Oclaro) for their support


  • Algorithm design and analysis
  • clustering
  • Clustering algorithms
  • coherent detection
  • coherent optical OFDM
  • Machine learning
  • nonlinearity mitigation
  • OFDM
  • Optical fiber amplifiers
  • Optical fiber networks
  • Phase shift keying


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