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
2018 Photonic network communications  
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
more » ... ceiver 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 (BER) and error vector magnitude (EVM) measurements. A good agreement on the performance of the proposed method with that of the Gram-Schmidt orthogonalization procedure (GSOP) is shown in a 20 Gbit/s optical QPSK experiment. The robustness of both methods was verified with up to 30 • phase imbalance by comparing the signal with and without phase imbalance compensation. A 10% reduction of EVM is achieved with our method for a high phase imbalance of 30 • while the implementation complexity can be reduced owing to the suppression of the use of square-root operators.
doi:10.1007/s11107-018-0783-7 fatcat:u6gjf74zhzguhbiuy6zsufzaku