Kenro Sekine

Incoherent 32-Level Optical Multilevel Signaling Technologies

In order to explore the potential of optical multilevel signaling for high-speed optical fiber networks, an incoherent 50 Gbit/s 32-level optical multilevel signaling (combination of QASK and 8-DPSK) is demonstrated, for the first time. The application of an ISI-suppressed modulation technique, an orthogonally-coupled differential detection technique and the digital signal processing technique have also been proposed and verified to enhance the performance of multilevel signaling. A 100-km dispersion shifted fiber transmission has also been performed, and the degradation via optical fiber nonlinear effect, self-phase modulation (SPM), is observed. The receiver side simple digital cancellation technique of the SPM-induced phase shift is also proposed and experimentally demonstrated with more than 6.8 dB increase of fiber input power.

Performance of chromatic dispersion monitoring using statistical moments of asynchronously sampled waveform histograms

The performance of the chromatic dispersion monitoring method using statistical moments of asynchronously sampled waveform histograms is investigated in detail. We show its robustness against signal-to-noise ratio degradation and its wide monitoring range using experiments and a newly developed numerical simulation method. We also show the effectiveness of radio frequency bandwidth reduction of the waveform monitor to widen its monitoring range, and also estimate its performance with duobinary and return-to-zero modulation formats.

Study on cross-phase modulation (XPM) effect on amplitude and differentially phase-modulated multilevel signals in DWDM transmission

The characteristic degradation mechanism of the cross-phase modulation (XPM) effect on multilevel amplitude and differentially phase-shift keying (APSK) signals in dense wavelength-division-multiplexing (DWDM) transmissions is analyzed and experimentally investigated, for the first time. Based on the results, we successfully demonstrate a 0.48-Tb/s (30-Gb/s/ch) 50-GHz-spaced 16-channel DWDM 160-km unrepeatered transmission of eight-level APSK signals suppressing the XPM-induced degradation.

A Novel Bias Control Technique for MZ Modulator with Monitoring Power of Backward Light for Advanced Modulation Formats

We propose a novel high-sensitive and cost-effective bias control scheme for MZ modulator with minimizing monitored power of backward-traveling light, and demonstrate its effectiveness with the experiments of 10-Gbit/s CSRZ and 43-Gbit/s RZ-DQPSK signals.

Multilevel Signalling for High-Speed Optical Transmission

Rapidly evolving multilevel signalling is a serious candidate of the next generation modulation format for high-speed and high-capacity optical communication links. In this paper, we review the recent progress of multilevel signalling technologies.

Proposal of Inter-Symbol Interference (ISI) Suppression Technique for Optical Multilevel Signal Generation

A virtually ISI-free optical multilevel modulation technique applicable to wide-range of multilevel formats is proposed. Superior QASK modulation performance is experimentally demonstrated with 3-dB sensitivity improvement in 40-Gbit/s 16-level amplitude- and phase-shift keying (APSK) modulation.

Investigation of cross phase modulation (XPM) effect on amplitude- and phase-modulated multi-level signals in dense-WDM transmission

The XPM effect on optical 8-ary APSK (amplitude- and phase-shift keying) multi-level signals is experimentally investigated, for the first time. Its feasibility is demonstrated in 0.48 Tbit/s (30 Gbit/s/ch) 50-GHz-spaced 16-channel dense-WDM 160-km unrepeatered transmission.

Modulation/Demodulation Schemes for Optical Multi-Level Transmission

The optical multilevel signaling is a promising candidate to realize next-generation high-speed transceivers beyond 40 Gbit/s, or ultimate-capacity DWDM system. This paper discusses advanced modulation/demodulation schemes toward the practical implementation of more than 16-level signaling.

Impact of cross-phase modulation on WDM transmission over dispersion-shifted fiber

Summary form only given. In summary, we performed a l0-Gbit/s four-channel transmission and verified that the cross phase modulation (XPM) combined with typical variation of fiber dispersion can significantly degrade the WDM transmission performance over dispersion shifted fiber (DSF), for the first time.

Modulation parameter tolerance for 8- and 16-APSK (amplitude- and phase-shift keying) signals

We investigate the impact of non-ideal modulating condition on multilevel APSK modulations, and find 4-% angular misalignment of orthogonal PSK components or residual chirp of 0.2 in ASK modulator causes 1-dB penalty of PSK components