Takayuki Nyu

Formation of the refractive index profile in the graded index polymer optical fiber for gigabit data transmission

Bandwidth characteristics of the large core graded index polymer optical fiber (GI-POF) are theoretically and experimentally clarified. The refractive index profile of the GI-POF was controlled by interfacial-gel polymerization to investigate the relation between the index profile and the bandwidth characteristics. It was experimentally confirmed that the maximum bandwidth of the poly methyl methacrylate (PMMA) base GI-POF is at most 3 GHz for 100 m transmission using a typical laser diode emitting at 650-nm wavelength (3 nm source spectral width) when its refractive index profile is optimized. The maximum bandwidth theoretically estimated by considering both modal and material dispersions is approximately 3 GHz which is exactly the same as the measured value, while higher than 10 GHz for 100 m was expected if only modal dispersion was taken into account. The optimum refractive index profile of the PMMA base GI-POF is theoretically and experimentally clarified by considering the profile dispersion further.

Fast Ethernet system with high-speed plastic optical fiber data links

In summary, we have achieved a 156 Mbps 100-m transmission with low numerical aperture (NA) step index plastic optical fiber (SI-POF) and low launch NA red LED. By using these technologies, a POF-based fast Ethernet system was successfully demonstrated. This system exhibited the advantages of cost and EMI tolerance of a POF link.

Development of Battery and Charger Integration System (BCIS) for EV charging stations

The popularization of electric vehicles (EVs) will give rise to challenges that include expenses for capacity upgrades, power supply shortages, and long waiting time to charge. We have therefore developed a Battery & Charger Integration System (BCIS) to support the burgeoning infrastructure for EVs. The system enables charging time reductions in simultaneously multiple EVs charging by shifting the charging power peak and using power of stationary batteries. This paper outlines the BCIS and the results of an experiment and simulation of charging time reductions.

A Radio Network Co-design System for Planning, Operation, and Customer Relations Divisions

Radio network planning after the initial rollout phase has a multitude of individual coverage and capacity problems. Such problems are often exposed by customer complaints or performance indicator degradations, so cooperation among network planning, operation, and customer relations divisions will help to more effectively improve network quality. In this paper, we propose to introduce radio network co-design by multiple divisions for sharing their issues and discussing possible solutions in the same place. To realize network co-design, we developed methods of 3D visualization of radio quality for enhancing comprehension of geographically dependent radio problems, high-speed prediction of radio propagation for interactive network planning, and estimation of radio resource usage for mutual understanding of the outcome of radio planning. Finally, we demonstrate an interactive wireless network design prototype system based on these methods.

IEEE1394 S200 infrared wireless adapter

We have demonstrated the worlds first IEEE1394 S200 infrared (IR) wireless adapter and verified its operation. Our adapters enable us to communicate using low cost devices with sufficient eye-safety margin. Further, we have indicated a design approach to reach a transmission distance of 10 m while keeping an easy alignment property.

Development of an IEEE 1394 long-haul adapter

We have developed a 1394 long-haul adapter that extends the distance between equipment up to 500 m while maintaining interoperability with existing 1394 devices. The adapter can be applied to the 1394-based home network and local area network.