title: Unrepeated 200-km transmission of 40-Gbit/s 16-QAM signals using digital coherent receiver.
abstract: We demonstrate unrepeated 200-km transmission of 40-Gbit/s 16-QAM signals using a digital coherent receiver, where the decision-directed carrier-phase estimation is employed. The phase fluctuation is effectively eliminated in the 16-QAM system with such a phase-estimation method, when the linewidth of semiconductor lasers for the transmitter and the local oscillator is 150 kHz. Finite-impulse-response (FIR) filters at the receiver compensate for 4,000-ps/nm group-velocity dispersion (GVD) of the 200-km-long single-mode fiber and a part of self-phase modulation (SPM) in the digital domain. In spite of the launched power limitation due to SPM, the acceptable bit-error rate performance is obtained owing to high sensitivity of the digital coherent receiver.
authors.affiliation: Department of Electronic Engineering, The University of Tokyo, Tokyo, Japan. mori@ginjo.t.u-tokyo.ac.jp
authors.forename: Yojiro
authors.initials: Y
authors.lastname: Mori
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.forename: Koji
authors.initials: K
authors.lastname: Igarashi
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Katoh
authors.forename: Kazuro
authors.initials: K
authors.lastname: Kikuchi