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 NguyenEmail author
  • Pascal Scalart
  • Mathilde Gay
  • Laurent Bramerie
  • Christophe Peucheret
  • Fausto Gomez-Agis
  • Olivier Sentieys
  • Jean-Claude Simon
  • Michel Joindot
Original Paper


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.


Coherent communications Fiber optical communications IQ imbalance Modulation 



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
    Email author
  • 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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