title: Analyses of wavelength- and polarization-division multiplexed transmission characteristics of optical quadrature-amplitude-modulation signals.
abstract: We theoretically study optical transmission characteristics of wavelength-division multiplexed (WDM) and polarization-multiplexed (POLMUX) signals using high-order optical quadrature-amplitude-modulation (QAM) formats up to 256. First, we conduct intensive computer simulations on bit-error rates (BERs) in WDM POLMUX QAM transmission systems and find maximum transmission distances under the influence of nonlinear impairments. Next, to elucidate the physics behind such nonlinear transmission characteristics, we calculate the distribution of constellation points for QAM signals as functions of the the launched power, the transmission distance, and the symbol rate. These results lead to a closed-form formula for BER of any QAM formats. From such formula, we derive simple laws that determine the maximum transmission distance and the optimum power as functions of the QAM order and the symbol rate. These laws can well explain the simulation results.
authors.affiliation: Department of Electrical Engineering and Information Systems, The University of Tokyo, Tokyo, Japan. kikuchi@ginjo.t.u-tokyo.ac.jp
authors.forename: Kazuro
authors.initials: K
authors.lastname: Kikuchi