Japan researches access networks and terabit backbones

By PAUL MORTENSEN

Japan has begun to focus on new types of devices called micro-opticalelectromechanical systems (moemss) for possible application in the access network. Researchers there are also working on the implementation of a terabit-per-second backbone, where success will depend on the progress of the Femtosecond Project, Japan`s longest national research project.

moemss combine free-space optics with optoelectromechanical sensing and actuating elements. One application could be optical alignment of fibers using microstructures.

Researchers are now looking at the possibility of mass-fabrication of micro-optical and micro- mechanical elements on the same wafer by using integrated batch processing techniques. Such integration, according to Nippon Telegraph & Telephone (ntt), could significantly improve the performance and reliability of many optical communications systems, as well as reduce their size, volume, and cost. Other applications for moemss could include optical data storage, display systems, laser manipulation, and near-field optical probe microscopy.

This range of applications was explored at moems `97, the first international conference on these systems, which was held last November in Nara, Japan. Communications and networks emerged as the strongest markets for moemss, with possible applications including optomechanical switching, free-space micro-optics, and microactuators. In this latter application, moemss could facilitate on-chip optical alignment, optomechanical integrated circuits, adjustable external cavity lasers, optical network devices (such as high-speed modulators and optical fiber connectors) and optomechanical switches based on optical fibers, optical waveguides, and movable mirrors.

Devices based on moemss, when they are available, may be used in optical access networks, possibly in fiber-to-the-home applications. Although a cost acceptable to ntt for fiber-to-the-office and to multiple-dwelling units was reached in 1997, ntt foresees that an acceptable cost for fiber-to-the-home will not be achieved until 2005 to 2010. The key technical issue to sufficiently reducing the cost of the optical network unit that connects the network to the individual user is optical coupling. moemss or associated integration technologies may provide the key to such cost reductions.

Ultrashort pulses

Meanwhile, plans for implementing a terabit-per-second backbone in about 10 years depends on the progress of the Femtosecond Project. Run by the Femtosecond Technology Research Association (festa), a joint research and development organization, the project began in December 1995 and will continue through 2004. festa`s budget was 395 million yen in FY96 and 1506 million yen in FY97.

The Agency of Industrial Science and Technology and its executive agency, the New Energy Development Organization, commissioned a management board that supervises festa and has links with the concerned national laboratories: the Electrotechnical Laboratory and the National Research Laboratory of Metrology. festa, however, remains the center of collaboration with the national laboratories and with university research laboratories.

The main points of research are generation and propagation technologies for ultrashort light pulses, switching and distribution technologies for these pulses, and fundamental technologies for femtosecond devices, e.g., ultrafast solid-state sources, femtosecond laser diodes, and laser and metrological technologies.

For ultrashort pulse optoelectronics, the goal is to develop ultrafast optoelectronic devices for terabit signal processing and transmission. The application is the optical fiber network in the terabit-per-second range planned for about 2010. The goal is 5 Tbits/sec over 100 km by 2015 (see Lightwave, December 1997, page 1).

The central research location is in Tsukuba; distributed research units are located in festa`s member companies, including Fuji Xerox Co. Ltd., Fujitsu Ltd., Hitachi Ltd., Kyocera Corp., Lucent Technologies Inc., Matsushita Research, Institute Tokyo Inc., Mitsubishi Electric Corp., nec Corp., Oki Electric Industry Co. Ltd., Panasonic Technologies Inc., Sumitomo Heavy Industries Ltd., Toshiba Corp., and the Institute of Research and Innovation.

The Ministry of Posts and Telecommunications (mpt) has its own plans to develop a 1-Tbit/sec optical communications system in cooperation with universities and private firms. In April 1996, the ministry established a research center in Sendai, supervised by Tohoku University president Nishizawa. The center is to be the core of a team of 50 researchers from universities, mpt research institutions, and private companies. mpt intends to spend a total of 60 billion yen (US$478 million) on this five-year project.

Despite Japan`s near-zero economic growth and Asia`s economic crisis, these research programs remain fully funded and strong. Nevertheless, with about 40% of Japan`s net exports headed for Asia, some sectors of research funding may come under pressure later this year. q

Paul Mortensen writes on Asian photonic and fiber-optic technology from Australia.