Together with Pioneer Micro Technology Corporation, Koshin Kogaku Co., Ltd., and Optoquest Co., Ltd., Professor Hiroyuki Tsuda, Associate Professor Ryogo Kubo, and other members at Keio University’s Faculty of Science and Technology were the first in the world to successfully demonstrate the transmission of ultra-high-definition (4K) videos using a new communication wavelength band called the T-band.
The T-band used in optical communication has wavelengths of between 1,000 and 1,260 nm. Compared with the C-band (1,530–1,565 nm) and L-band (1,565–1,625 nm), which are normally used in optical fiber transmissions, the T-band has greater transmission loss, making it impractical to send transmissions over long distances. For this reason, the T-band was not used for optical fiber transmissions. However, with the spread of cloud computing, as well as services that provide ultra-high-definition videos in recent years, there has been a rapid increase in demand for short- to medium-range optical communication technology. These distances are in the tens of kilometers and applications include datacenter and access networks. For this, there are high expectations for the T-band, which can provide over 1,000 wavelength channels at a frequency spacing of 50 GHz. In this research, optical components for the T-band —quantum dot gain chip, wavelength tunable laser, semiconductor optical amplifier, and arrayed waveguide grating— were developed, and using these, a wavelength routing system was built. Furthermore, using this newly built wavelength routing system, the transmission of 4K videos was demonstrated. Through the effective use of the massive wavelength resource of 80 THz, which was produced by combining the T-band and the adjacent O-band (1,260–1,360 nm), an expansion in transmission capacity and increase in scalability were seen in short- and medium-range optical networks. There is great expectation for this technology to contribute to the introduction and promotion of new services.
The achievements of this research were presented at the 43rd European Conference on Optical Communication (ECOC 2017), an international conference held in Gothenburg, Sweden on September 21, 2017 (local time).
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World’s First Successful Transmission of Ultra-High-Definition (4K) Videos through a Newly Defined Wavelength Band Named “T-Band” 
