Kazuho Ohara

OTDM transmitter using WDM-TDM conversion with an electroabsorption wavelength converter

An all-optical multiplexing technique using wavelength division multiplexing (WDM)-time division multiplexing (TDM) conversion with an electroabsorption wavelength converter has been proposed and demonstrated. The effectiveness of this WDM-TDM conversion technique for various pulsewidth settings was experimentally investigated. The fluctuation of the signal performance, which was inevitably caused by the coherent crosstalk between adjacent pulses in the conventional optical time division multiplexing (OTDM) technique, were successfully suppressed, even in the case of wide pulse duration. High Q-factor performance has been maintained for a wide range of duty ration from 36% to 74%. By introducing this technique to the optical time division multiplexer, a highly stable and high-quality 40-Gb/s optical signal can be effectively produced without generating the short pulse or setting two tributaries at orthogonal polarization states, and without introducing high-speed electronics for signal multiplexing. The WDM-TDM conversion with an electroabsorption wavelength converter was extended to 60-Gb/s operation by using three 20-Gb/s tributaries. A clear eye opening was confirmed for a waveform after the WDM-TDM conversion of the 60-Gb/s signal.

Traffic analysis of Ethernet-PON in FTTH trial service

Applicability of Ethernet-PON systems providing real-time broadband services such as video streaming and voice over IP to the commercial FTTH service has been confirmed through the traffic analyses in the FTTH field trial.

Highly reliable optical bidirectional path switched ring networks applicable to photonic IP networks

The reliability of the optical bidirectional path switched ring (OBPSR) network is studied by using optical networking equipment (ONE) with microelectromechanical system (MEMS)-based optical switching fabrics. The reliability of the wavelength path in OBPSR networks is shown to be highly dependent on redundant schemes of switching fabrics in the ONE. This study proposes a new redundant scheme utilizing optical couplers together with controlled switch fabrics without using active selectors, and shows that reliability of the wavelength path can be remarkably improved. A fast redundant switching operation of 10 ms was experimentally confirmed with a prototype of the ONE based on the proposed redundant switching fabrics. Furthermore, interworking operations in terms of the protection and restoration between the optical layer and the Internet protocol (IP) layer are experimentally investigated. In a 500-km optical ring network, fast wavelength path protection switching was confirmed without reconfiguring the link state database of the IP layer, and the measured protection time in the IP layer was as short as 21 ms.

Fairness of downstream TCP throughput among diversely located ONUs in a GE-PON system

A method for providing fairness of the downstream TCP throughput among diversely located ONUs in a GE-PON system has been proposed and has been successfully demonstrated by using a GE-PON with 32 ONUs placed at 2 km and 50 km.

60 Gbit/s WDM-OTDM transmultiplexing using an electro-absorption modulator

We propose a WDM-OTDM transmultiplexing technique to generate a stable high speed OTDM signal with adjustable pulse width by using an electro-absorption modulator and demonstrate 60 Gbit/s signal generation from three 20 Gbit/s WDM signals.

Performance analysis of Ethernet PON system accommodating 64 ONUs

Feature Issue on Passive Optical Network Architectures and TechnologiesWe report the performance of an IEEE 802.3 standard compliant Ethernet passive optical network (EPON) system accommodating 64 optical network units (ONUs). After investigating the optical transmission performance, we successfully demonstrate that a high throughput of more than 900Mbits/s can be achieved in a 64-ONU EPON system using multiple logical link identifiers per ONU within a range of 10km. In addition, we confirm the feasibility of IP-based high-quality triple play services in the EPON system.

Demonstration and performance analysis of gigabit-Ethernet PON system accommodating 64 ONUs

We have demonstrated a two-wavelength gigabit-Ethernet PON system accommodating 64 ONU, and have evaluated its performance to clarify the feasibility of commercial applications. We have confirmed that high-quality triple play services can be achieved with high throughput.

Reliability of optical bi-directional path switched ring networks using MEMS-based redundant switching fabrics

We have shown that the reliability of optical networks highly depends on the redundant scheme of all-optical switching fabrics in optical switching nodes, and achieved remarkable improvement of the reliability by introducing new 1+1 redundant scheme using optical couplers. Active components can be eliminated from optical interfaces. The proposed redundant scheme was implemented using MEMS matrix switches, and fast protection switching of less than 10 milliseconds was confirmed.

Failed ONU detection technique applicable to commercially available passive optical networks

We propose and demonstrate a failed ONU detecting method by controlling ONUs to periodically transmit with MPCP frames of commercially available EPON. Proposed method can specify failed ONUs even when disturbing lights are higher by 18 dB than normal ONUs.

Performance analysis of downloading speed on token-passing based PON system

We have analyzed performance of the PON system adopting token passing for achieving high downloading speed. A virtue of the token passing has been revealed by numerical calculations.