title: Adaptive threshold adjustment for signal-distortion-free digital-coherent optical demodulation system.
abstract: Optical quadrature amplitude modulation (QAM) attracts considerable attention in the enhancement of communications capacity, due to its high spectral efficiency. However, this modulation format is more sensitive to signal distortion than conventional formats, making it more difficult to create, transmit, and detect signals. In this paper, we propose an adaptive scheme for demodulation of the distorted optical signals with paying attention to use of DSP-technology. The scheme is based on the adjustment of the thresholds against the signal distortion. Successful demodulation of optical QAM signals is demonstrated with a sufficiently low bit-error rate.
authors.affiliation: Advanced Device Research Group, New Generation Network Research Center, National Institute of Information and Communications Technology, 4-2-1, Nukui-Kitamadchi, Koganei, Tokyo 184-8795, Japan. chiba@nict.go.jp
authors.forename: Akito
authors.initials: A
authors.lastname: Chiba
authors.forename: Takahide
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kawanishi