Daisaku Ogasahara

Novel RZ signal format with alternate-chirp for suppression of nonlinear degradation in 40 Gb/s based WDM

A novel alternate-chirped RZ signal format is proposed. 2 dB improvement in nonlinear tolerance has been confirmed experimentally, compared to CS-RZ format in 40 Gb/s based WDM-480 km transmission experiment with 100-GHz channel spacing.

Real-time evaluation of optical nonlinear effects on 112Gbps PM-QPSK signal in dispersion managed links

We demonstrate the impact of nonlinear effects on dispersion managed links with a FPGA-based 112Gbps real-time receiver. We clarify that PM-RZ-QPSK provides superior robustness, whereas PM-NRZ-QPSK offers better total performance resulting from higher OSNR sensitivity.

112Gb/s optical transponder with PM-QPSK and coherent detection employing parallel FPGA-based real-time digital signal processing, FEC and 100GbE Ethernet interface

We demonstrate 112Gb/s transmission using PM-QPSK format and FPGA-based real-time digital signal processing. By employing framed processing architecture for polarization demultiplexing and carrier phase estimation, stable operation of error free after FEC and wide frequency offset have been achieved.

Hardware-efficient polarization demultiplexing for QAM signals based on dual stage decision-directed algorithm

We propose a hardware-efficient polarization demultiplexing algorithm suitable for QAM signals, which is based on dual decision-directed algorithm. Our algorithm requires only half size hardware of a conventional double stage algorithm based on CMA.

Transmission of a 127 Gb/s PM-QPSK signal over a 3350 km SMF-only line with chromatic dispersion compensation using real-time DSP [Invited]

We experimentally confirmed the effectiveness of chromatic dispersion compensation by overlap frequency-domain equalization in real-time digital signal processing for a 127 Gb/s polarization-multiplexed quadrature phase shift keying (PM-QPSK) signal up to 56,200 ps/nm. We verified a penalty lower than 0.55 dB for accumulated dispersion over a 3350 km single-mode-fiber- (SMF-) only transmission line. We also demonstrated the transmission of a 127 Gb/s PM-QPSK signal in a 50-GHz-spacing 5-channel wavelength division multiplexing configuration over the same SMF-only line with a received Q factor of 10.1 dB.

Mitigation of intra-channel nonlinear distortions based on PAPR reduction with CD pre-compensation in real-time 50Gbps PM-QPSK transmission

We verified the correlation between PAPR and intrachannel nonlinear distortions with 50.7Gbps PM-QPSK signal over 1,310km dispersion non-managed transmission. Experimental results with 50% CD pre-compensation exhibited minimal PAPR and improved Q factor.

Improving ethernet reliability and stability using global open ethernet technology

In this paper, authors present new schemes of our proposed Global Open Ethernet (GOE) technology from a viewpoint of improving reliability in metro-area Ethernet environment and show the numerical evidence on their performance results. Although several standardized or vendor proprietary technologies are proposed to improve Ethernet reliability, they still have reliability problems in terms of long failure recovery time (due to forwarding database (FDB) flush and recovery from a root bridge failure on spanning tree protocol), broadcast storm, and packet loss in network reconfiguration. To solve these problems, we introduce three schemes, a Per Destination - Multiple Rapid Spanning Tree Protocol (PD-MRSTP), a GOE Virtual Switch Redundancy Protocol (GVSRP), and an In-Service Reconfiguration (ISR) schemes. PD-MRSTP scheme reduces the failure recovery time by eliminating the need to flush the FDB and to recover from root bridge failures. GVSRP scheme ensures the reliability of connections between a GOE domain and a legacy Ethernet domain. Combined with PD-MRSTP, GVSRP prevents broadcast storm problems due to loops in the inter-domain area. ISR scheme enables in-service bridge replacement and upgrade without packet loss. Evaluating our prototype system, we obtained the following remarkable performance results. The GOE network using PD-MRSTP scheme delivered a fast failure recovery performance (4 ms) independent of the number of MAC address entries, whereas the legacy Ethernet network took 522 ms when a bridge had 6000 MAC address entries. Since we found that the failure recovery time increased in proportion to the number of MAC address entries, the one in large carrier network having one million of MAC address entries would take several tens of seconds. Thus using PD-MRSTP can reduce failure recovery time one ten-thousandth comparing with that of legacy Ethernet. In addition, evaluation of the ISR scheme demonstrated that a network can be upgraded with zero packet loss. Therefore, a GOE-based VPN is a promising alternative to other Ethernet VPNs for its reliability and stability.

Experimental verification of minimum overlap size design in a FDE-based chromatic dispersion compensation circuit with a 50Gb/s PM-QPSK signal

We propose a simple design method of minimum overlap data size for overlap-FDE based CD compensation. We confirmed its validity using a real-time DSP circuit and 50.7Gbps PM-QPSK signal for up to 56,200ps/nm.

Expansion of system dynamic chromatic-dispersioncompensation range by optimal FIR filter adaptation

A novel method for FIR filter control optimization is proposed to expand the chromatic dispersion compensation range in electrical digital signal processing systems in transmitters and receivers. A reduction of the number of coefficients of FIR filter by 40% is observed, which allowed to reduce the instability occurred by mis-configuration during the filter control.