We have developed a cost-effective regional personal-computer (PC) communication network system based on fiber-to-the-home (FTTH) systems and examined its realization. The system provides a LAN environment and group communication services to the customers. The intelligent bridge circuit, called the low-end card (LEC), is set up in the subscriber's household. The LEC provides the popular Ethernet interface (10Base-T). The leased circuits are connected between the LEC and the center brouter (bridging router). The LEC and the brouter are controlled by the management server to function as the group communication system. The brouter, which has a multiplex subscriber-port interface, is required to accommodate a lot of customers cost effectively. This paper presents the system design of a multiplex-port brouter with SDH/SONET interface. The brouter can accommodate about 2000 subscribers. Ethernet packets are transferred through each subscriber channel between the LEC and the brouter using the HDLC protocol. A group communication mechanism based on packet filtering via the MAC addresses of PCs is presented. The Ethernet packets are filtered by the brouter to eliminate all packets except those from/to the same group members. The implementation of the group management function into the center brouter and the customers premises LEC is discussed. The traffic reduction effect by the brouter is also estimated from experimental results.

The development and system design of a new synchronous DS4 multiplexer with cross-connect function is described. This new multiplexer is expected to provide cost reductions due to more efficient use of transmission facilities, and rapid circuit provisioning. The multiplexer consists of three kinds of digital cross-connect blocks, a transmission terminating block, an intraoffice-interface block, and a controler. It is also expected to provide improved network maintenance, higher network reliability, and greater system versatility for new services.

This paper considers the requirements of, and proposes technical solutions for, the optical transmission modules used in intraoffice links. A novel crosstalk noise measurement procedure is proposed along with a quantitative evaluation method for crosstalk prevention which is very important in the development of compact modules. A procedure for circuit adjustment elimination is also proposed, previously a great obstacle to attaining low manufacturing costs. Based upon the above, two types of modules are developed for DS2 and DS3 signal transmissions which meet the requirements of small size, low power consumption, and low cost without transmission performance degradation.