Yasuharu Suematsu

In 1993, he was elected a member of the National Academy of Engineering (US) with the award citation "For contributions to the understanding and development of optical fibers, high performance semiconductor lasers, and integrated optoelectronics.

[7] The earliest demonstration of optical fiber communication was performed by Suematsu and his students, on May 26, 1963, on the occasion of the open house of the Tokyo Institute of Technology (Fig.1).

The original ADP reserved in the desiccator as well as the replica of that experiment, restored in 2008-7 as shown in Fig.1, was registered as a Future Technology Heritage, at the National Museum of Science, Japan, in 2019.

Following these preliminary achievements, Suematsu and his co-workers succeeded in creating an integrated laser with built-in distributed reflectors using a material in the band of 1.5 micrometres.

Thus, the thermo-tunable dynamic single-mode laser was born and triggered to develop a 1.5-micrometer high-speed fiber system, as cited by such as the 1983 Valdemar Poulsen Gold Medal, the Danish history of optical communication, and the 1986 David Sarnoff Award.

The actualization of the dynamic single-mode laser became an impetus to develop high-capacity and long-distance optical fiber communications, and it began to be applied commercially at the end of the 1980s.

Later, the tuning wavelength range was increased by the introduction of distributed reflectors with multi-grating pitches by Yuichi Tohmori and Yuhzou Yoshikuni, and Larry Coldren.

Phase shift distributed feedback lasers developed by this research have been commercially applied for long distances—for overland trunk systems (1987) and for intercontinental submarine cables (1992) (Fig.

Optical fiber communications have progressed and the Internet has developed, and instantaneous transmission of a large volume of knowledge is now a daily occurrence.

In contrast, the proliferation of high-capacity and long-distance optical fiber communications has allowed for large-volume information such as books to become used interactively in an instant.

Fig.1. Replica of the earliest demonstration of optical fiber communication experiment, on May 26, 1963, restored in 2008-7. [ clarification needed ] (Registered as Future Technology Heritage, at the National Museum of Science, Japan). By courtesy of the Museum of Tokyo Institute of Technology.
Fig.2. Principle of Single-mode resonator consisted of two distrusted reflectors connected with phase shift of integer multiple of Π/2, for Dynamic Single Mode (DSM) Lasers, in 1974.
Fig.3. Laser tip on the mount of the first demonstration of dynamic single mode laser at a wavelength of 1.5 micrometers, in October 1980. By courtesy of the Museum of Tokyo Institute of Technology.
Fig.4. Single-mode property and schematic structure of the first demonstration of dynamic single mode laser at wavelength of 1.5 micrometers, in October 1980.
Fig.5 Schematic structure of Phase-Shift Distribute Feedback laser, in October 1983 ~Thermo-tunable Dynamic Singlr Mode Laser ~.
Fig.6. A commercial phase shift distributed reflector laser array, with 100\ coin for size reference. By courtesy of Furukawa Electric Co.
Fig.7. Schematic structure of Wavelength Tunable Laser ~ Electro, in 1980 ~Electro-tunable Dynamic Single Mode Laser ~.
Fig.8. International submarine cables around the world. By courtesy of KDDI.
Fig.9. Transmission performance of communication fiber. Prime data by Courtesy of NTT & KDDI.