1 Department of Photonics Engineering, Technical University of Denmark2 Metro-Access and Short Range Systems, Department of Photonics Engineering, Technical University of Denmark3 Department of Informatics and Mathematical Modeling, Technical University of Denmark4 Coding and Visual Communication, Department of Photonics Engineering, Technical University of Denmark5 Cognitive Systems, Department of Informatics and Mathematical Modeling, Technical University of Denmark6 Department of Applied Electronics, Technical University of Denmark7 Technical University of Denmark8 Department of Applied Mathematics and Computer Science, Technical University of Denmark9 Huawei Technologies
In this paper, we show numerically and experimentally that expectation maximization (EM) algorithm is a powerful tool in combating system impairments such as fibre nonlinearities, inphase and quadrature (I/Q) modulator imperfections and laser linewidth. The EM algorithm is an iterative algorithm that can be used to compensate for the impairments which have an imprint on a signal constellation, i.e. rotation and distortion of the constellation points. The EM is especially effective for combating non-linear phase noise (NLPN). It is because NLPN severely distorts the signal constellation and this can be tracked by the EM. The gain in the nonlinear system tolerance for the system under consideration is shown to be dependent on the transmission scenario. We show experimentally that for a dispersion managed polarization multiplexed 16-QAM system at 14 Gbaud a gain in the nonlinear system tolerance of up to 3 dB can be obtained. For, a dispersion unmanaged system this gain reduces to 0.5 dB.
Optics Express, 2012, Vol 20, Issue 26
Main Research Area:
38th European Conference and Exhibition on Optical Communication, 2012