title: Experimental analysis of singularity-avoidance techniques for CMA equalization in DP-QPSK 112-Gb/s optical systems.
abstract: We experimentally investigate the singularity problem in DP-QPSK 112-Gb/s receivers using the CMA. Three algorithms are compared: Constrained, Two-Stage, and Multi-User. Although these algorithms have been individually evaluated, they have not been compared by extensive experiments. The transmission setup emulates amplifier noise; first-order PMD; and chromatic dispersion. It is shown that all algorithms effectively mitigate singularities. However, under certain conditions, the Multi-User and the Constrained algorithms--both used for system startup--outperformed the Two-Stage, which does not distinguish between system operation and startup. In light of its effectiveness and low computational complexity, we recommend the Constrained algorithm.
authors.affiliation: OCNLab, Department of Electrical Engineering, University of Brasilia, Brazil.
authors.forename: Valery N
authors.initials: VN
authors.lastname: Rozental
authors.forename: Thiago F
authors.initials: TF
authors.lastname: Portela
authors.forename: Diego V
authors.initials: DV
authors.lastname: Souto
authors.forename: Hugo B
authors.initials: HB
authors.lastname: Ferreira
authors.forename: Darli A A
authors.initials: DA
authors.lastname: Mello