EIAJ Demos Video, Audio Transmission At 400Mbits/second

By Yoshiko Hara, EE Times

13-Apr-00

Aiming at a low-cost fiber network with an IEEE 1394 interface for the home, a project group headed by the Electronic Industries Association of Japan (EIAJ) has demonstrated audio and video data transmission at rates of 400Mbits/second. The data was transmitted over a polymethylmethacrylate plastic optical fiber (POF) and traveled a distance of over 100 meters. ""For future home-network applications, 400Mbit/sec speed [which is the highest speed defined by the IEEE 1394 interface at present] is necessary,"" said EIAJ project leader Yasuhiro Koike, a professor at Keio University. ""Such networks linked with home servers have to handle large-volume signals such as digital TV broadcasting."" When a home network handles multiple channels of video and audio signals, even the IEEE 1394 interface's highest speed will eventually be insufficient to meet demand, Koike said. A low-cost network can be implemented using plastic optical fiber, but it has speed disadvantages. With the achievement of actual audio and video data transmission at the rate of 400Mbits/sec, however, Koike said he believes the IEEE 1394 interface will expand beyond such current limited uses as digital video cameras. 650nm Laser TappedA graded-index (GI) POF and a 650-nanometer semiconductor laser were used to achieve the high speed and greater distance. Keio University has been studying the graded-index POF, which has a high refractive index at its core that continuously decreases as it approaches the periphery. That structure is different from a step-index (SI) plastic fiber, which is in use now. The step-index fiber has a two-layer structure comprising the core and an outer, surrounding layer. The core has a high refractive index and the outer layer has a low refractive index. The light reflects at the boundary between the core and the outer layer, which causes it to spread out. Graded-index fiber does not have a boundary, and thus the pulse maintains its shape over long distances. Koike said his group at Keio University has nearly completed development of the graded-index plastic fiber, and that it is almost ready for volume production. ""GI fiber is suitable for high-speed transmission, but for consumer applications, SI fiber is enough to achieve a certain level of performance because it is available now and is inexpensive,"" said an engineer of an electronics manufacturer that is not a member of the EIAJ project. NEC Corp. started offering an optical module with an SI-type POF based on the 1394 spec last fall. The module transmits signals at a maximum of 250Mbits/sec over 50 meters. Sharp Corp. and Sony Corp. are jointly pursuing development of a compact form of an SI-type POF and a connector. Their first prototype transmitted signals at 125Mbits/sec last fall over a 10-meter distance. The POF effort is part of a 1999 project for common infrastructure development of data systems in the home conducted by Japan's Ministry of International Trade and Industry. The project is supported by eleven companies: Hitachi, Inforcity, Kenwood, Matsushita Electric Industrial, Mitsubishi Electric, ProMedia, Sanyo Electric, Seiko Epson, Sky Think System, Techno Scope and the Victor Co. of Japan. The project group will present its findings April 25 at Keio University.