On August 29, NTT and Kitami Institute of Technology (KIT) jointly announced that, using a single optical fiber for communication, they successfully supplied over 1 watt of electrical power to an area devoid of electricity located more than 10 kilometers away, while maintaining high speed and good communication quality. Before this attempt, an optical fiber could only transmit a power of 1 watt over a distance of approximately 1 kilometer; however, the developed fiber could transmit the same power over 14 kilometers, enabling high-speed communication. Thus, both communication and optical power feeding could be realized using a single optical fiber. The results of the above study will be presented at the 49th European Conference on Optical Communications (ECOC 2023), the world's largest international conference on optical communications to be held in Scotland and to be announced on October 4.
The optical fiber used in the experiment had a diameter of 125 micrometers, the same thickness as the optical fiber currently adopted for use in communications. The structure and dimensions of the fiber conformed to international standards, and the transmission capacity was equivalent to that of existing optical fibers. The technical key point was the development of a multi-core optical fiber with four cores, capable of supplying a power more than four times that supplied by conventional optical fibers. In the experiments, the developed multi-core optical fiber supplied more than 1 watt of power to a distance of 14 kilometers, delivering an optical power of 14 watt・kilometer (14 kilometers x 1 watt).
Different light (wavelength) sources were used for optical power feeding and optical communication. In particular, light with a wavelength of 1,550 nanometers was used for power feeding, and that with a wavelength of 1,310 nanometers was used as the signal light for communication. This enabled the successful realization of two-way high-speed optical communication by feeding power from a transmitter/receiver within a communication building with a power source to a remote transmitter/receiver without a power source located 14 kilometers away.
Furthermore, during this study, the two parties conducted a two-way optical communication experiment with a transmission speed of 10 gigabits per second by self-feeding power and confirmed good transmission characteristics after the 14-kilometer-transmission. Considering the product of the transmission speed and distance as an index of the transmission characteristics through the self-feeding power, the attempt demonstrated the world's highest transmission characteristics of 140 Gbps×km.
The results of this experiment are significant, as the experiment used a multicore optical fiber with characteristics equivalent to those of the optical fibers currently in use. For practical applications, existing optical fiber communication systems can be used as they are without any upgrades. The developed optical fiber was demonstrated to be useful not only for normal long-distance high-speed optical communication but also for two-way optical communication with optical power feeding. With the development of this optical fiber, communication equipment located in areas where power restoration during disasters or emergencies is difficult can be driven by feeding power light from the communication building, consequently improving network resilience.
In future, this development is expected to facilitate optical communications in areas such as non-electrified areas including rivers and mountainous regions, as well as areas where electrification is difficult owing to strong electromagnetic fields and corrosion. NTT and KIT plan to continue to promote their research and development efforts through industry-academia collaborations to further improve the optical power feeding capacity.
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.