Atsuki Taniguchi

Digital optical CATV system using hubbed distribution architecture

A hubbed distribution architecture based on a bus-star configuration, three-level single single-mode fiber transmission using M-TPC line code, and high-speed IC technology is proposed. The architecture is cost-effective and compact. It is well suited to metropolitan area CATV systems and would allow a gradual transition to a broadband ISDN (integrated-services digital network) subscriber loop in the future. The proposed architecture is applied to a digital optical CATV system prototype. The equipment making up this system consists of a transmitter, hubs including video selectors, and subscriber unit. Two video channels are selected for each subscriber from eight video channels at hub stations. The transmission speed is 900 Mb/s, three-level for the trunk line and 200 Mb/s, three-level for each subscriber loop. Very compact and low-cost equipment is realized by using recently developed high-speed ICs. Experimental results show that the system satisfies requirements and that its commercial application is feasible. >

Flexible synchronous broad-band subscriber loop system: optical shuttle bus

A flexible, synchronous, broadband subscriber loop system called the optical shuttle bus is discussed. The emphasis is on the proposed design architecture and performance of a 1.8-Gb/s prototype system. The optical shuttle bus is constructed of multigigabit/second intelligent optical shuttle nodes (OSNs). The software-defined OSNs allow the bus to be configured as a synchronous transmission network with any topology and provides flexible channel allocation by means of a drop/insert/cross-connect function. The OSN can be configured as a highly reliable network by virtue of its self-healing functions such as line switch, bypass, and loop back. The proposed bus architecture has been successfully applied in a 1.8-Gb/s prototype in which three OSNs are connected by one 10-km and two 5-dm single-mode fibers in a ring configuration. Very compact and inexpensive equipment is realized by using high-speed ICs. Experimental results show the proposed architecture to be a powerful one for the realization of synchronous broadband subscriber loop systems. >

Gigabit single-mode fiber transmission using 1.3-µm edge-emitting LEDs for broad-band subscriber loops

This paper describes gigabit single-mode fiber transmission using 1.3-μm edge-emitting LEDs for broad-band subscriber loops, focusing on a method of calculation for maximum transmission distance and 1.2-Gbit/s and 600-Mbit/s transmission experiments. Gigabit single-mode fiber transmission is necessary for subscriber loops, especially in broad-band ISDN and optical CATV systems. Edgeemitting LEDs are excellent light sources because of their high power launched into the fiber compared with surface-emitting LEDs, and currently lower cost and higher reliability than laser diodes. The maximum transmission distance is carefully estimated by taking into account the wavelength dependence for both chromatic dispersion and loss of the single-mode fiber, and the possibility of gigabit transmission near the dispersion free wavelength 1.3 μm, is confirmed. Encouraged by the above results, we demonstrate 1.2-Gbi,t/s 10-km and 600-Mbit/s 20-km transmission experiments using a newly developed 1.3-μm edge-emitting LED and a new driver circuit with a simple response compensation circuit. These results show the proposed calculation method and the LED response compensation circuit to be powerful tools for the realization of low-cost gigabit single-mode fiber transmission using edge-emitting LEDs.

Experimental broadband drop/insert/cross-connect system: 1.8 Gbit/s optical shuttle bus

An optical shuttle bus architecture to realize a flexible synchronous interoffice and subscriber-loop network is proposed. An experimental broadband drop/insert/crossconnect system with SONET interfaces, called the 1.8-Gb/s optical shuttle bus, is then described. The bus is constructed of multigigabit intelligent optical shuttle nodes (OSNs). The software-defined OSN can be configured as any synchronous transmission network topology and provides flexible channel allocation by means of the drop/insert/crossconnect function. The OSN can also be configured as a highly reliable network by using self-healing functions, such as line switch, bypass, and loop back. Laboratory testing of an experimental system, consisting of three OSNs with one 10-km and two 5-km single-mode fibers in a ring configuration, has confirmed the practicality of the proposed architecture.<<ETX>>

32-channel digital optical CATV distribution system

The authors discuss a digital optical CATV system with increased channels, focusing on its network configuration, WDM and TDM (wavelength and time division multiplexing) schemes, and its application to a 32-channel CATV distribution system. The key technologies for low-cost increased-channel CATV are discussed, and the economical number of TDM channels and the required interchannel isolation in the WDM demultiplexer are clarified. Bit-synchronized compensation for the propagation delay differences in WDM is proposed, as is a new multiplexing scheme suitable for low-power, compact TDM equipment. A compact 32-channel TDM and WDM video distribution system was designed based on a bus-star configuration and newly developed high-speed LSI technology. The transmission characteristics of the transmitter/receiver equipment developed for feeder loops were found to be good, and experimental results show that the proposed design with its versatile hardware will be a powerful tool for a low-cost multichannel digital optical CATV system.<<ETX>>