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Photonic Network Communications

, Volume 36, Issue 3, pp 326–337 | Cite as

New metric for IQ imbalance compensation in optical QPSK coherent systems

  • Trung-Hien Nguyen
  • Pascal Scalart
  • Mathilde Gay
  • Laurent Bramerie
  • Christophe Peucheret
  • Fausto Gomez-Agis
  • Olivier Sentieys
  • Jean-Claude Simon
  • Michel Joindot
Original Paper
  • 64 Downloads

Abstract

We report on a simple alternative method for the compensation of quadrature imbalance in optical quadrature phase-shift-keying (QPSK) coherent systems. By introducing a new metric, the phase imbalance can be determined and compensated. The proposed method is theoretically and numerically analyzed. In particular, it is shown that the method exhibits a small bias of estimated phase imbalance value. Thanks to its deterministic property, this bias can be simply compensated by incorporating at the receiver a phase rotator (or phase shift) whose value can be determined based on an analytical analysis. Moreover, the algorithm is also experimentally validated through bit-error-rate and error vector magnitude (EVM) measurements. A good agreement on the performance of the proposed method with that of the Gram–Schmidt orthogonalization procedure is shown in a 20-Gbit/s optical QPSK experiment. The robustness of both methods was verified with up to \(30^\circ \) phase imbalance by comparing the signal with and without phase imbalance compensation. A 10% reduction in EVM is achieved with our method for a high phase imbalance of \(30^\circ \), while the implementation complexity can be reduced owing to the suppression of the use of square-root operators.

Keywords

Coherent communications Fiber optical communications IQ imbalance Modulation 

Notes

Acknowledgements

This work was supported by the French National Research Agency (ANR) in the frame of the OCELOT Project (Ref. ANR-10-VERS-0015), the Contrat de plan Etat-Région Ponant and the French Ministry of Research.

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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Trung-Hien Nguyen
    • 1
    • 3
  • Pascal Scalart
    • 2
  • Mathilde Gay
    • 1
  • Laurent Bramerie
    • 1
  • Christophe Peucheret
    • 1
  • Fausto Gomez-Agis
    • 1
    • 4
  • Olivier Sentieys
    • 2
  • Jean-Claude Simon
    • 1
  • Michel Joindot
    • 1
  1. 1.FOTON Laboratory, CNRS, ENSSATUniversity of Rennes 1LannionFrance
  2. 2.INRIA/IRISAUniversity of Rennes 1RennesFrance
  3. 3.OPERA DepartmentUniversité Libre de BruxellesBrusselsBelgium
  4. 4.Department of Electrical EngineeringTechnische Universiteit EindhovenEindhovenThe Netherlands

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