Highlights

- Developed a multi-core fiber cable consisting of eight 4-core, standard cladding diameter multi-core fibers

- Introduced a multi-core fiber transmission unit into a real system handling uncompressed 8K video

- Enabled ultra-high-capacity data transmission through existing conduits and limited interior space within buildings

Abstract

The National Institute of Information and Communications Technology (NICT, President: TOKUDA Hideyuki Ph.D.) the Advanced ICT Research Institute, ASTRODESIGN, Inc. (President and CEO: NANBA Toyoaki), and Fujikura Ltd. (Director, President and CEO: OKADA Naoki) have developed a multi-core fiber cable consisting of eight 4-core, standard cladding diameter multi-core fibers, and they have successfully implemented it for the first time as an ultrahigh-capacity data transmission unit in a real system handling uncompressed 8K video.

In an uncompressed 8K video system, approximately 70 Gbps of data must be transmitted per video stream, requiring one single-core single-mode fiber for each uncompressed 8K camera. The developed multi-core fiber cable contains a total of eight standard cladding diameter (125 μm) single-mode 4-core multi-core fibers of two different types within a 3 mm diameter cable, which is equivalent to the 32 single-core single-mode fibers that are conventionally used in uncompressed 8K video systems.

In this implementation, by introducing a transmission unit that utilizes the multi-core fiber cable, we successfully achieved stable system operation by transmitting high-volume video data from multiple 8K cameras installed in a cleanroom, through limited-capacity information conduits and building interior spaces, over 300 m to an 8K video composition device located in a separate building.

This achievement enables the deployment of systems requiring high-capacity data transmission, such as uncompressed 8K video systems, even in cases in which conventional installation was difficult owing to limited space in information conduits or wiring pathways within or between buildings.

Background of the Development

In recent years, 8K video has begun to be used in applications such as television broadcasting and cinema. Particularly in sports broadcasting, there is a growing shift from the conventional approach of deploying numerous cameras throughout a stadium to a method in which a small number of 8K cameras capture the entire scene and the desired portions are extracted and used via image processing. This method has become feasible only because of the ultrahigh resolution of 8K video. Because 8K video offers ultrahigh resolution, it is increasingly being explored for applications beyond television broadcasting and cinema, including telemedicine, simulators for aircraft, and competitive automobiles.

In pursuit of Research DX initiatives, NICT has been promoting the introduction of 8K video systems into cleanrooms. Introducing 8K video for monitoring in cleanrooms enables detailed surveillance of areas far from the camera, comprehensive monitoring of wide areas, and high-resolution observation beyond the capabilities of the naked eye. This further enables the rapid identification of the precise locations of problems and facilitates an accurate understanding of the nature of these problems when they arise.

Uncompressed 8K video enables ultrahigh-resolution imaging in real-time without delay, thus making it possible to observe device fabrication processes in greater detail than with the naked eye and offering potential for applications such as remote collaborative experiments. Moreover, uncompressed 8K video requires data transmission of approximately 70 Gbps per stream, necessitating the use of one single-core single-mode fiber for each uncompressed 8K camera. Therefore, many optical fiber cables are required as the number of cameras increases. In modern buildings, conduit systems within and between structures are typically already filled with numerous Ethernet and power cables, which leaves insufficient space to accommodate the installation of additional optical fiber cables. This issue regarding space has posed a significant challenge to the implementation of 8K video systems.

8K Video System

The 8K video system implemented in the cleanroom consists of an uncompressed 8K camera, a compressed 8K camera, a multi-core fiber transmission unit, an 8K video composition device, an 8K video control device, and an 8K monitor, among other components (see Figure 1).

The uncompressed 8K camera and 8K video composition device are connected bidirectionally via the multi-core fiber transmission unit. The captured uncompressed 8K RAW data, LAN signals, and other control signals are transmitted as 12-wavelength CWDM signals (1,270, 1,290, 1,310, 1,330, 1,350, 1,370, 1,470, 1,490, 1,510, 1,530, 1,550, and 1,570 nm), with six wavelengths each allocated for uplink and downlink. These signals are bidirectionally multiplexed within a single-core single-mode fiber, achieving a total bidirectional transmission rate of 69.3 Gbps. The uncompressed 8K video is combined with other 8K video streams within the 8K video composition device and then output to the 8K monitor via the 8K video control device.

The compressed 8K cameras compress the captured video and output it as compressed 8K video at a rate of 40 Mbps per camera. In the present 8K video system, 32 compressed 8K cameras are connected to the 8K video composition device using 3 sets of SFP-10GLR-31 modules and a total of 6 cores from 6 single-mode fibers. Within the 8K video composition device, the video is combined with other 8K video streams and then output to devices such as 8K monitors via the 8K video control device.

In the 8K video system implemented in the cleanroom, 9 out of the total 32 compressed 8K cameras are routed through the video composition device to enable the simultaneous viewing of multiple video streams on the 8K monitor. The remaining 23 cameras provide a viewing experience that simulates walking through the cleanroom in real-time by using virtual reality (VR) glasses.

All these video streams can be viewed in real-time, requiring both an environment capable of high-speed transmission and the processing of multiple ultra-high-resolution 8K video streams without delay. Therefore, the transmission unit that enables high-capacity data transfer within limited spaces and the processing system capable of handling large volumes of data without delay are built using dedicated hardware.

Achievements

(1) Developed a multi-core fiber cable consisting of eight 4-core standard cladding diameter multi-core fibers

In contrast to conventional fibers, which contain only one core, a multi-core fiber is an advanced technology that contributes to increased transmission capacity and higher cable density by incorporating multiple optical signal transmission cores within a single optical fiber. The multi-core fiber used in this work contains four cores within the same glass cladding diameter (125 μm) and coating diameter (250 μm) as conventional single-mode fibers.

In multi-core fibers, a major challenge is controlling inter-core crosstalk, a phenomenon in which signals leaking from adjacent cores intrude into neighboring cores, which causes interference and degradation of signal quality. The 4-core standard cladding diameter multi-core fiber developed in this work was designed by optimizing the core arrangement and optical properties to reduce inter-core crosstalk. This 4-core standard cladding diameter multi-core fiber has been realized by applying the design and fabrication technologies developed through NICT’s Commissioned Research Project 20301, “Development and Research for Accelerating the Practical Implementation of Multi-Core Fibers” (2018–2022), under the Advanced Communication and Broadcasting R&D Program.

Figure 2 shows an overview of the multi-core fiber cable. This cable contains a total of eight 4-core standard cladding diameter multi-core fibers within a 3 mm outer coating and enables information transmission equivalent to that provided by 32 conventional optical fibers. Additionally, for testing purposes, the cable incorporates two types of multi-core fibers with different inter-core crosstalk characteristics. Furthermore, optical connectors are terminated at both ends of the multi-core fibers to allow for integration with imaging systems and short-range systems via multi-core fiber multiplexers/demultiplexers (MUX/DEMUX).

(2) Implemented a multi-core fiber transmission unit in a real system handling uncompressed 8K video

As shown in Figure 1, a transmission unit utilizing the multi-core fiber cable was developed and introduced into the 8K video system to enable the transmission of high-volume video data from multiple 8K cameras installed in a cleanroom, through limited-capacity information conduits and interior spaces, over 300 m to an 8K video control device located in a separate building, thereby making system operation possible.

The transmission unit using the multi-core fiber cable consists of a multi-core fiber cable containing eight 4-core standard cladding diameter multi-core fibers along with multi-core fiber MUX/DEMUX that connect each 4-core standard cladding diameter multi-core fiber to four conventional single-core optical fibers. The multi-core fiber multiplexer/demultiplexer was developed by the collaborating company OPTOQUEST CO., LTD. (President: HIGASHI Noboru).

The multiplexer/demultiplexer (see Figure 3) uses a micro-optical coupling system with miniature lenses to connect each core of the multi-core fiber to four single-mode fibers in a non-contact manner. The advantage of this method is that each single-mode fiber can be individually and optimally aligned to the corresponding core of the multi-core fiber, which allows for extremely low coupling error and thus low loss. Moreover, this configuration is adaptable to multi-core fibers with varying core counts and core pitches. Furthermore, because no adhesives or similar materials are used to bond optical components in the optical path, the system offers high reliability and excellent power handling characteristics. In addition, YAG laser welding, which is a method with a proven track record in highly reliable optical communication components, is used to secure each component.

Moreover, the multi-core fiber cable and multi-core fiber multiplexers/demultiplexers are equipped with multi-core fiber connectors that facilitate easy interconnection between multi-core fibers.

The MUX/DEMUX for multi-core fibers and the interconnection technology between multi-core fibers are based on the outcomes of NICT’s Commissioned Research Project 150: “R&D on Innovative Optical Communication Infrastructure: Multi-Core Fiber Interconnection Technology—Establishment of Input/Output Optical Device for Technology for multi-core fiber—” (2011–2015), under the Advanced Communication and Broadcasting R&D Program.

(3) Installed the multi-core fiber cable through existing information conduits and limited interior spaces within buildings to enable the stable operation of a real 8K video system involving ultra-high-capacity data transmission

Many optical fiber cables are required between the cameras and video composition device, among other connections, as the number of ultra-high-definition 8K cameras increases, in modern buildings, conduit systems within and between structures are typically already filled with numerous Ethernet and power cables, leaving insufficient space to accommodate the installation of additional optical fiber cables. This issue of space has posed a significant challenge to the implementation of 8K video systems.

In this work, a transmission unit using a multi-core fiber cable suitable for deployment in real systems was developed and introduced into an 8K camera system. As a result, high-volume video data from multiple 8K cameras installed in a cleanroom were successfully transmitted over 300 m, through limited-capacity information conduits and interior spaces within buildings, to an 8K video composition device located in a separate building. Thus, stable system operation was achieved.

In Figure 4(a), the yellow line represents a single 3 mm diameter multi-core fiber cable, and the white lines represent eight 4-core standard cladding diameter multi-core fibers (equivalent to 32 single-mode fibers). Figure 4(b) shows the multi-core fiber cable installed via routing through a narrow existing wiring path, where modifications to the building structure are restricted, while avoiding interference with other pre-installed cables. Figure 4(c) shows the interior of a relay box in which the multi-core fiber cable has been installed. Because the number of cables can be drastically reduced, the multi-core fiber cable can be installed, even within limited space inside the relay box, significantly improving maintainability. Furthermore, communication cables that previously required large quantities and substantial wiring lengths (such as Ethernet cables) can be drastically consolidated, offering the potential for reduced power consumption and space savings (see Figure 4(d)).

This achievement enables the deployment of systems that require high-capacity data transmission, such as uncompressed 8K video systems, even in cases in which conventional installation is difficult owing to limited space in information conduits or wiring pathways within or between buildings.

Future Prospects

Utilizing the newly developed multi-core fiber transmission unit enables the deployment of systems that require high-capacity data transmission, such as uncompressed 8K video systems, even in environments where conventional deployment is difficult owing to limited conduit or wiring space within or between buildings. Going forward, we will pursue further research and development aimed at expanding the range of applications through increased core density in multi-core fiber cables and the significant miniaturization of transmission and reception devices.

Roles of Each Organization

- NICT: Design of the overall system, including the multi-core fiber transmission section, and coordination of the entire project

- ASTRODESIGN, Inc.: Development and implementation of the 8K video system

- Fujikura Ltd.: Development of the 4-core standard cladding diameter multi-core fiber and multi-core fiber cable

Article Information

Fujikura Ltd.

Journal: 2023 Optical Fiber Communications Conference and Exhibition (OFC)

DOI: 10.1364/OFC.2023.M3B.5

Title: Characteristics of Over 600-km-Long 4-core MCF Drawn from a Single Preform

Authors: Shota Kajikawa, Tsubasa Saito, Katsuhiro Takenaga, and Kentaro Ichii