Distinguished Researcher
Taiji Sakamoto

Next generation optical fiber for realizing ultra-large capacity communication

--Please tell us about the research fields, research projects, and research themes that you are currently engaged in.

I am currently engaged in the research of next-generation optical fiber to support the ultra-high-capacity, ultra-high-speed network of the future. Today, the data transmission capacity flowing through the network is increasing at an annual rate of several tens of percent, and the prediction is that it will reach a level in the latter half of the 2020s that can longer be accommodated even by optical fiber (single-mode fiber) that has been supporting the trend toward higher capacities in recent years. For this reason, given that the limit in transmission capacity of currently deployed optical fiber is on the order of 1 Tbit/s (1 terabit = 1012 bits), our goal is to achieve optical fiber capable of a transmission capacity of 1 Pbit/s (1 petabit = 1015 bits) or higher. Specifically, my main research target is space division multiplexing (core multiplexing plus mode multiplexing) using multi-core/multi-mode fiber having multiple optical paths within a single optical fiber. This research involves the optimization of optical-fiber structure and the conducting of performance evaluation tests.

--Please tell us how your research themes involve "top-level innovative research and pioneering technology development."

In our research group, we have been researching optical fiber for use with space division multiplexing from early on and have been reporting world-class performance indices at international conferences and other gatherings. As part of these efforts, I have been focusing on coupled-core type multi-mode fiber that achieves a peculiar type of optical propagation different than that within single-mode fiber. I have taken a leading position in the world in explaining this propagation mechanism and have shown that this type of fiber has a performance potential more than ten times higher that of existing optical fiber. In designing a new fiber structure, it is not enough to simply design a structure that can increase capacity. In other words, the new structure must simultaneously satisfy a number of requirements, such as mechanical reliability applicable to the NTT network, high space division multiplexing efficiency for efficient use of the limited space available for communication facilities, and reduction of deviation in signal quality between optical transmission signals. With these requirements in mind, my goal has been to achieve top performance indices. The structure under study constitutes a new system that could not be achieved by existing optical-fiber design technology. It is a field that also requires the study of a variety of peripheral technologies. In my research team, we are focusing on candidate technologies that can have an even greater impact over the long term and on innovative and comprehensive studies that include not only optical fiber technologies but also peripheral technologies (such as transmission system evaluation and low-power relay technology). We aim to achieve a communications platform that will bring about revolutionary changes in the NTT network.

--In what way will the promotion of your research themes change the world and how would you personally like to change the world?

Optical fiber is a vital component that supports the NTT network from its location in the network infrastructure. Its influence on the network is significant and far-reaching. Optical fiber technology itself, though not visible to the end user on the surface, will have an ever-increasing impact as the future foundation of information-communication services. I myself would like to use the optical fiber that we have researched and developed to support the creation of many innovative application services and to solve social problems as in dealing with the ever-increasing amount of power consumed by communication systems. In this way, we can contribute not only to a transformation of the NTT network but also to real social change. I envision a sustainable optical network lasting for several tens of years that will enable the business ventures and lives of many people to flourish through information-communications.