TOKYO, July 2, 2026 — In a milestone development for global telecommunications infrastructure, a collaborative research team has successfully demonstrated high-quality, high-power optical signal transmission exceeding 10 watts (W) using hollow-core fiber (HCF) technology. This achievement, part of the “Research and Development Project of Advanced Optical Transmission Technology Contributing to a Green Society,” marks a pivotal shift in how we might power the next generation of 5G and IoT networks while simultaneously expanding data capacity.
The joint research effort, spearheaded by the University of Electro-Communications, Lightera Japan Co., Ltd., and Keio University, addresses one of the most persistent bottlenecks in modern optical networking: the physical limitations of silica-core optical fibers. By utilizing HCF, which guides light through an air-filled center rather than solid glass, the team has effectively bypassed the nonlinear interference that has historically capped the power levels of optical communications.
Main Facts: The 10-Watt Milestone
The core of this breakthrough lies in the successful integration of wavelength-multiplexing into a Passive Optical Network (PON) system using Lightera’s proprietary hollow-core fiber. In traditional silica-core fibers, increasing the optical power leads to significant nonlinear effects—phenomena where the signal waveform distorts, causing errors and limiting data throughput. Because these distortions occur within the glass medium, there is a strict "ceiling" on how much light can be pushed through a single fiber.
By switching to a hollow-core architecture, the researchers reduced these nonlinear effects to roughly 1/1000th of those found in conventional fiber. This dramatic reduction allowed the team to transmit 5G NR signals at 28 GHz across four multiplexed wavelengths at an input power exceeding 10 W. This is not merely a theoretical gain; it is a practical demonstration of high-quality data transmission at energy levels previously considered impossible for standard optical infrastructure.
Chronology: The Road to the Hollow-Core Revolution
The development of this technology did not happen in a vacuum. It is the culmination of years of research aimed at aligning the needs of a "Green Society" with the insatiable demand for high-speed, low-latency connectivity.
- Early 2020s: As 5G deployment accelerated, researchers identified a massive surge in the number of wireless base stations required to support high-frequency bands. The energy and cabling requirements for these "small cell" networks began to pose a logistical and environmental challenge.
- The Commissioning: The Ministry of Internal Affairs and Communications (Japan) launched the “Research and Development Project of Advanced Optical Transmission Technology Contributing to a Green Society (JPMI00316),” providing the framework and funding for universities and industry partners to collaborate.
- Mid-2025: The research group successfully refined the hollow-core fiber manufacturing process, enabling lower-loss transmission suitable for long-haul testing.
- Late 2025 – Early 2026: Laboratory testing began, focusing on the integration of OLT (Optical Line Terminal) and splitter components into the HCF-based PON system.
- June 2026: The team successfully achieved the 10W threshold, validating that high-power signals could be transmitted without sacrificing the integrity of the 5G NR data stream.
- July 2, 2026: Formal announcement of the breakthrough, with publication scheduled for the August 2026 issue of the Journal of Optical Communications and Networking.
Supporting Data: Understanding the Physics and Scale
To understand the significance of this development, one must look at the technical specifications of the system:
The Nonlinear Effect Barrier
In standard single-mode silica fibers, the high intensity of light within the solid core creates a nonlinear refractive index. This causes "self-phase modulation" and "four-wave mixing," which scramble the data encoded on the light waves. By transmitting light through an air-filled core, the HCF removes the glass-light interaction that triggers these nonlinearities.
PON Scaling Capabilities
The research indicates that this new transmission method could support over 4,096 branches in a single PON system. In current networks, the splitting ratio is often constrained by the power budget of the optical signal. By significantly increasing the allowable input power, the network can reach a vastly larger number of wireless base stations and IoT sensors without requiring additional fiber runs, drastically reducing the "physical footprint" of urban telecommunications.
5G NR Compatibility
The test utilized a 28 GHz carrier frequency—a staple of high-speed 5G communications. Successfully transmitting this complex modulation at 10 W without signal degradation proves that the system is ready for real-world integration into high-bandwidth mobile networks.
Official Responses and Perspectives
The Role of Lightera Group
As the technology provider, Lightera Group—the global arm of the Furukawa Electric Group’s optical solutions—emphasized the importance of material innovation. "The hollow-core fiber is not just a different type of cable; it is a fundamental shift in transmission medium," noted a spokesperson for the research group. "By moving from glass to air, we are essentially moving from a restrictive medium to an open highway, allowing for both data and power to coexist."
The Academic Vision
Professor Motoharu Matsuura of the University of Electro-Communications, who led the research, highlighted the dual-purpose nature of the system. "Our goal was to solve two problems at once: capacity and resilience. If we can use the same fiber to send data and provide the electrical power required to run the base station, we create a network that can survive even when the local power grid fails. This is a critical component for future disaster-resilient communications."
The team at Keio University’s Future Photonic Network Open Lab underscored the importance of the 5G/IoT ecosystem. "The ability to scale to thousands of branches means we can connect entire neighborhoods of IoT devices through a single, high-capacity, low-latency backbone," stated the research leads.
Implications: A Greener, More Resilient Future
The implications of this breakthrough extend far beyond the laboratory.
1. Optical Fiber Power Supply (OFPS)
Perhaps the most transformative application is the ability to use the fiber optic line to deliver power. By transmitting light as energy, the system can convert optical power into electrical power at the receiver side. This removes the need for copper wiring for base stations, which is prone to electromagnetic interference and corrosion. In the event of a disaster, if the central office (the OLT) has a backup power source, it can keep remote base stations running through the optical fiber, ensuring critical communication remains available.
2. Reduced Infrastructure Costs
The deployment of 5G and 6G requires a dense network of small cells. Traditionally, this requires laying both fiber for data and power cables for energy. By consolidating these functions, the HCF-PON system significantly reduces the cost of trenching, installation, and ongoing maintenance.
3. Energy Efficiency and Sustainability
The "Green Society" initiative mentioned in the commissioning is directly addressed by this technology. By reducing the number of active power-consuming devices in the field and optimizing the efficiency of the transmission, the network consumes less energy overall. Furthermore, the material properties of hollow-core fiber lead to lower latency—approximately two-thirds the delay of silica fiber—which is essential for real-time applications like autonomous driving and remote surgery.
4. Future Outlook: Beyond 5G
As the researchers plan to multiplex more wavelengths over a wider spectrum, the capacity of this system will only grow. The upcoming publication in the Journal of Optical Communications and Networking will provide the technical community with the blueprints for this expansion, likely triggering a new wave of research into high-power optical networking components.
Glossary of Terms
- PON (Passive Optical Network): A fiber-optic network architecture that uses unpowered optical splitters to enable a single optical fiber to serve multiple endpoints.
- Hollow-Core Fiber (HCF): A revolutionary type of optical fiber where the core is air-filled, allowing for higher power limits and lower latency compared to glass cores.
- Nonlinear Effect: The distortion of light signals caused by high power levels within a solid glass medium.
- Optical Fiber Power Supply: A method of sending energy through fiber optics to provide power to remote, hard-to-reach hardware.
- 5G NR (New Radio): The global standard for the air interface of 5G mobile networks, particularly effective in high-frequency bands like 28 GHz.
For further inquiries regarding this research, please contact the Public Relations sections of the University of Electro-Communications, Lightera Japan Co., Ltd., or Keio University.
