Kenkichi Shimomura

70-GHz-spaced 40/spl times/42.7 Gb/s transpacific transmission over 9400 km using prefiltered CSRZ-DPSK signals, all-Raman repeaters, and symmetrically dispersion-managed fiber spans

70-GHz-spaced 40/spl times/42.7 Gb/s prefiltered carrier-suppressed return-to-zero differential phase-shift keying (CSRZ-DPSK) signals have been transmitted over transpacific distances for the first time, using all-Raman repeaters with two pump-wavelengths, dispersion-managed fiber commercially available in volume, and an ETDM receiver. In this paper, first, in order to enhance the spectral efficiency, the impact of bandlimitation to a CSRZ-DPSK signal was experimentally investigated in comparison to a conventional CSRZ-on-off-keying (OOK) signal, and we found that the bandlimitation tolerance of CSRZ-DPSK signal was smaller than that of CSRZ-OOK signal in back-to-back condition. We also confirmed that the prefiltering CSRZ-DPSK signal with up to 65 GHz bandlimitation potentially had better transmission performance than the prefiltered CSRZ-OOK signal. In addition, we found that, although the nonlinear transmission penalty was increased by bandlimitation, this penalty for CSRZ-DPSK signal was smaller than that for CSRZ-OOK signal. Through this study, long-term stability of the transmission performance was also evaluated with low-speed signal polarization scrambling without using any polarization mode dispersion (PMD) compensation.

Frequency stabilized 622-Mb/s 16-channel optical FDM system and its performance in 1.3/1.55-/spl mu/m zero-dispersion fiber transmission

A study has been conducted on a densely multiplexed 16-channel optical FDM system. A transmitter contains 16 two-section MQW DFB-LDs and a star coupler. An automatic optical multi-frequency controller stabilizes each LD of 10 GHz spacing within /spl plusmn/100-MHz accuracy. A receiver consists of heterodyne-delay-demodulators using a polarization diversity. Any desired channel can be tuned by a novel frequency discriminator with no insensitive frequency region. The system has successfully transmitted 622 Mb/s-16-channel HDTV signals through 110 km long 1.3 /spl mu/m-zero-dispersion fiber. We have also studied error rate degradation due to four-wave mixing in a 1.55 /spl mu/m-dispersion-shifted-fiber. Experimental results have revealed the allowable total input power to be +2 dBm for dispersion-shifted fibers. >

A fully integrated block turbo code FEC for 10 Gb/s optical communication systems

A block turbo code FEC compatible with G.709 has been fully integrated on VLSI. Combining this with a 3-bit soft decision ASIC enabled a net coding gain of 10.1 dB at 12.4 Gb/s with 23.6% redundancy.

Automatically tracked dispersion compensation with penalty-free tunable dispersion equalizer for 40 Gbit/s systems

The automatic control of a tunable dispersion equalizer by means of a bit error monitor was demonstrated. The tunable dispersion equalizer developed consists of a chirped fiber grating and divided thin film heaters. From the tests of the step response and the automatic DEQ control, we confirmed that the tunable dispersion equalizer based on the grating and heaters is suitable for adaptive dispersion compensation of dispersion variations caused by slowly varying environmental conditions with a fluctuation rate of several minutes or more.