Kazuyuki Ishida

A comparative study of DPSK and OOK WDM transmission over transoceanic distances and their performance degradations due to nonlinear phase noise

We have compared experimentally the transmission performance of return-to-zero differential phase-shift keying (RZ-DPSK) with RZ-ON-OFF keying (OOK), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK), and NRZ-OOK for 100/spl times/10-Gb/s transmission with a spectral efficiency of 0.22 b/s/Hz over transoceanic distances. The Q degradation of the RZ-DPSK after transmission over 9180 km was 3 dB greater than that of RZ-OOK. The experimental results clearly showed the major cause of degradation for DPSK is not cross-phase modulation but self-phase modulation. The calculated nonlinear phase noise, i.e., the Gordon-Mollenauer effect, agreed with the experimental results. A distributed-Raman-amplifier assisted erbium-doped-fiber-amplified transmission line acted well in reducing the nonlinear phase noise.

Spectrally-efficient dual phase-conjugate twin waves with orthogonally multiplexed quadrature pulse-shaped signals

We propose a novel nonlinearity mitigation technique which can double the spectral efficiency of a phase-conjugate twin wave by diplexing the twin waves. Simulation shows a Q improvement of 1.2 dB from conventional DP-QPSK transmission.

True PRBS transmission of DQPSK by differential precoder employing parallel prefix network

A novel differential precoder using a parallel prefix network for minimum circuit size and speed is proposed. We demonstrate 20 Gb/s RZ-DQPSK transmission of true PRBS31 using conventional gate arrays operating at only 78 Mb/s.

Effect of Modulator Bias Control in the Presence of a Finite Extinction Ratio in DQPSK Pre-Equalization Systems

The effect of the finite extinction ratio of a dual-parallel Mach-Zehnder modulator in 43-Gb/s differential quadrature phase-shift keying systems employing pre-equalization is reported. The degradation of the signal quality with 10000-ps/nm dispersion pre-equalization is 2.9 dB at an extinction ratio of 26 dB. We show that bias adjustment can improve the degradation due to a finite extinction ratio. The improvement at an extinction ratio of 26 dB is 2.2 dB. In practical pre-equalized systems, bias control is a key enabler for maintaining high signal quality.

A comparative study of 10 Gb/s RZ-DPSK and RZ-ASK WDM transmission over transoceanic distances

We have experimentally compared RZ-DPSK with RZ-ASK for 100/spl times/10 Gb/s transmission over transoceanic distances. The Q degradation of RZ-DPSK due to nonlinearity effects after transmission over 9180 km was 3 dB larger than that of RZ-ASK.

65 /spl times/ 22.8 Gb/s WDM transmission over 8,398 km employing symmetrically collided transmission with Aeff managed fiber

Two proposed methodologies, Aeff management and symmetrically collided transmission, were discussed for long haul transmission systems. 65 /spl times/ 22.8 Gb/s WDM transmission over 8398 km was achieved by employing these techniques.

Cycle Slip Compensation with Polarization Block Coding for Coherent Optical Transmission: Two-dimensional phases constellation corresponds to a slip state

Cycle slip (CS) compensation is a critical technique for nondifferential coded coherent optical transmission. By monitoring the sparse, asymmetric polarization block-coded symbol mapped signal phases of two orthogonal polarizations, the CS can be estimated from a relatively short stretch of symbols (unit). Simulation shows that the polarization block coding-based method compensates CS and improves the Q-factor by 1 dB or more compared to differential coding.

Adaptive Optical Compensation with Twin Fiber Gratings for First and Second Order PMD

Twin tunable chirped-fiber gratings and a DOP monitoring scheme provide adaptive PMD compensation for 40-Gbps RZ-DQPSK signals. We show quantitatively the compensation scheme improves the PMD tolerance, but its effect is limited by second-order PMD.