Kiyo Ishii

Monolithically integrated waveband selective switch using cyclic AWGs

We propose a novel waveband-selective switch that uses cyclic arrayed-waveguide gratings. The device is fabricated on one chip using planer lightwave circuit technologies. Tests demonstrate that the designed performance is successfully realized.

First demonstration of ultra-low-energy hierarchical multi-granular optical path network dynamically controlled through NSI-CS for video related applications

We developed ODU-XC, CDC-ROADM, and silicon photonics switch, and built an eight-node network capable of 90Tbps based on NSI-CS standard protocol. Its energy consumption was orders of magnitude lower than that achievable with IP routers.

Development of Hierarchical Optical Path Cross-Connect Systems Employing Wavelength/Waveband Selective Switches

We propose hierarchical optical path cross-connect (HOXC) system architectures that utilize wavelength selective switches (WSSs) and waveband selective switches. They are very compactly implemented compared to single-layer optical cross-connect systems that use only WSSs. We have developed a prototype of one of the proposed HOXC architectures and experimentally confirmed its feasibility.

Hierarchical optical cross-connect architecture that implements colorless waveband add/drop ratio restriction utilizing a novel wavelength multi/demultiplexers

We propose a novel compact hierarchical optical cross-connect architecture that implements the colorless waveband add/drop ratio restriction, and a novel MUX/DMUX that can be used by different wavebands. We show that the proposed cross-connect architecture can reduce switch scale significantly compared to conventional one. The function of the newly proposed MUX/DMUX is verified in an experimental system.

Energy consumption and traffic scaling of dynamic optical path networks

Dynamic path switching in lower layers such as optical or sub-wavelength layer-1 path connections is essential for future networks to provide end-to-end, bandwidth-guaranteed, large-capacity services without energy crunch. While this is almost generally agreed, the number of ports in optical switches tends to be limited by technological difficulties, severely restraining the scale of the network. However, video-related services, that occupies most of the traffic nowadays, could significantly alleviate such restraints if we utilized the nature of video usage. In most cases, video-related services are virtually provided through prior reservation scheme in which a relatively high call-blocking probabilities or long latency for a connection can be tolerated. This situation allows us to accommodate a relatively high number of subscribers with a limited number of switch ports. This paper shows that a network using optical switches with a technologically feasible number of ports, multi-granular paths, and a hierarchical network topology can be of a national scale accommodating several tens of millions of subscribers. The purpose of detailing a plausible network topology is to show that such a network offers a benefit of energy efficiency approximately three orders of magnitude compared with that extrapolated from recent router-based networks. We then discuss important technical aspects of such dynamic optical path networks including our several research activities. We emphasize the importance of vertically integrated research activities from application to device layers to develop the dynamic optical path networks.

Development of compact hierarchical optical path cross-connect prototype utilizing integrated colorless multi/demultiplexers

We introduce a compact matrix-switch-based hierarchical optical path cross-connect prototype system that exploits integrated colorless waveband multi/demultiplexers. Its performance ensures cost-effective networks can be created.

Ultracompact Waveband Cross-Connect Module Using Waveband Selective Switches: Development and Performance Verification

A compact waveband cross-connect switch module is demonstrated that will be utilized for creating cost-effective multidegree optical cross-connect nodes. Its performance confirms the practical applicability of the developed module.

Unifying Top-Down and Bottom-Up Approaches to Evaluate Network Energy Consumption

A novel method for estimating energy consumption of networks at the national scale is presented. Accurate estimations of network energy consumption are increasingly important because of continuously increasing network traffic and the need to assess emerging energy technologies to achieve overall energy efficiency. However, direct estimations are not practical because of the complex, widely diverse, and undisclosed configurations of actual networks. The impact of each networks energy overhead, which is the energy consumed above that required to accommodate network traffic, on the energy consumption associated with these complex configurations must be inferred. In the proposed method, the energy overhead is quantitatively evaluated and introduced as overhead factors by comparing the energy consumption estimated from network configuration models (bottom-up methods) with reports of actual energy consumption (top-down methods). This proposed “unified” method is capable of long-term predictions of future technology trends, including network architecture changes. In this paper, we consider different overhead factors that serve as fitting parameters for different network areas, and demonstrate the procedure for determining each of these parameters through an estimation of the fixed broadband Internet in Japan. This unified method consistently estimates the long-term evolution of energy consumption from 2000 to 2030.

Development of Hierarchical Optical Cross-Connect System for ROADM-Ring Connection Using PLC Technologies

An efficient reconfigurable optical add-drop multiplexer ring connecting node architecture is proposed that utilizes waveband routing; it achieves a small footprint and excellent cost-effectiveness. The key component devices are implemented using planar lightwave circuit technologies and their performances are verified in experiments.

Wavelength assignment dependency of AGC EDFA gain offset under dynamic optical circuit switching

Dynamic gain offsets in WDM AGC EDFAs caused by optical circuit switching are experimentally evaluated. A simple wavelength assignment policy can reduce the gain offsets by up to 0.7 dB after five cascaded EDFAs.