NTT Corporation has demonstrated a construction technology that allows various types of optical fibres to branch and merge without causing communication interruption. This result is expected to reduce the cost of facility construction and shorten the construction period for telecommunications carriers, especially as the number of connected devices in the Internet of Things continues to expand.
The development of a fabrication method for branched optical fibres with a structure of varying core diameters enables the use of optical fibres with various effective refractive indices. This innovation allows for branching of optical fibres regardless of their effective refractive index, overcoming previous challenges in optical network configuration. These results will be presented at the Tsukuba Forum 2024 to be held from 16-17 May 2024.
Background
With the advancement and spread of optical communication technology, various IT terminals are expanding in our daily lives. In line with this trend, various terminals such as radio base stations and sensors are expected to be connected to the network. This requires a flexible optical network that allows various terminals to connect quickly and easily. However, since it has not been possible to change the network configuration without interrupting communication, to connect terminals to a new location, it has been necessary to construct a new optical fibre cable or other network, which has resulted in high equipment construction costs and time required to open the network.
Technological challenges
Optical fibres used worldwide have various refractive index distributions and have different propagation characteristics (effective refractive index). Conventional technologies for branching these optical fibres require the same propagation characteristics (effective refractive index) for the optical fibre at the source and the optical fibre at the destination of the branch. Therefore, it was necessary to know the effective refractive index of the optical fibre at the branch source and to prepare an optical fibre for suitable branching. However, in order to grasp the effective refractive index, it is necessary to stop the service of the optical fibre at the branch source. Given this background, it has become a challenge to establish a technology that enables branching of optical fibres during communication regardless of their effective refractive index.
Key points of this achievement
NTT has developed a fabrication method for branched optical fibres with a varied core diameter structure. Since the effective refractive index varies with the core diameter, the optical fibre of this structure can be used as an optical fibre with various effective refractive indices. By using this structure as a branched optical fibre, it is possible to branch optical fibres regardless of the effective refractive index of the source optical fibre. NTT has demonstrated for the first time in the world the technology for fabricating this branched optical fibre. This greatly expands the range of optical fibres that can be branched compared to conventional optical fibres and has made it possible to branch and merge all optical fibres that meet the international standard commonly used in optical access networks.
Outlook
With this achievement, NTT has established technology to branch various optical fibres in communication without interruption. This technology is expected to enable the realisation of flexible optical networks that can be connected from anywhere without affecting communications. In addition, this innovation could enable telecommunications carriers to reduce facility construction costs and shorten construction periods, thereby making it possible to use the network earlier than before. NTT will continue to evaluate the environmental resistance characteristics and conduct field verification using prototype devices, aiming to realise a flexible optical network that can be connected from anywhere and respond quickly to diversifying customer needs.
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