title: Nonlinear impairment compensation using expectation maximization for dispersion managed and unmanaged PDM 16-QAM transmission.
abstract: 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.
authors.affiliation: DTU Fotonik, Technical University of Denmark, Build 343, DK-2800, Denmark. dazi@fotonik.dtu.dk
authors.forename: Darko
authors.initials: D
authors.lastname: Zibar
authors.forename: Ole
authors.initials: O
authors.lastname: Winther
authors.forename: Niccolo
authors.initials: N
authors.lastname: Franceschi
authors.forename: Robert
authors.initials: R
authors.lastname: Borkowski
authors.forename: Antonio
authors.initials: A
authors.lastname: Caballero
authors.forename: Valeria
authors.initials: V
authors.lastname: Arlunno
authors.forename: Mikkel N
authors.initials: MN
authors.lastname: Schmidt
authors.forename: Neil Guerrero
authors.initials: NG
authors.lastname: Gonzales
authors.forename: Bangning
authors.initials: B
authors.lastname: Mao
authors.forename: Yabin
authors.initials: Y
authors.lastname: Ye
authors.forename: Knud J
authors.initials: KJ
authors.lastname: Larsen
authors.forename: Idelfonso Tafur
authors.initials: IT
authors.lastname: Monroy