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Novel Transmission Technique Enables World Record 430 Tb/s in a Commercially Available, International-Standard-Compliant Optical Fiber

- Achieved with technique that multiplies the usable capacity of certain spectral regions by up to three times -
November 11, 2025

National Institute of Information and Communications Technology

Highlights

  • A new optical transmission record of 430 Tb/s, surpassing the previous record of 402 Tb/s.
  • The breakthrough leverages international-standard-compliant, cutoff-shifted optical fibers with a novel approach that triples the capacity of certain spectral regions using spatial-division multiplexing.
  • This innovation promises to enhance metropolitan networks and inter-datacenter links by offering high throughput with reduced complexity, while utilizing existing optical fiber infrastructure.
The National Institute of Information and Communications Technology (NICT, President: TOKUDA Hideyuki, Ph.D.), together with 11 international research partners, has demonstrated a record-breaking 430 terabits per second (Tb/s) optical transmission using a novel approach that extends the capacity of standard-compliant cutoff-shifted optical fibers well beyond the original design.
The technology introduces a novel method that multiplies the usable capacity of certain spectral regions by up to three times. This approach exploits the properties of standard-compliant cutoff-shifted optical fibers based on the ITU-T G.654 recommendation, which have been originally designed to operate with light at relatively long wavelengths, in the C and L bands of transmission bands. By using light with shorter wavelengths, in the O-band region, researchers were able to realize three-mode transmission instead of the traditional single-mode transmission. This effectively extended the optical fiber capacity well beyond the intended design by combining single-mode transmission in the E/S/C/L bands with three-mode transmission in the O band. The team achieved a new optical transmission record of 430 Tb/s in international-standard-compliant optical fibers, surpassing the previous our record of 402 Tb/s, which was also set in 2024. Remarkably, the new result was obtained using nearly 20% less overall bandwidth, resulting in a simpler system that demonstrates how existing infrastructure can be pushed even further without costly upgrades.
The new technology builds on standard-compliant cutoff-shifted optical fiber technology and has the potential to be applied to metropolitan area networks and inter-datacenter links, where high-capacity connections are increasingly in demand, and standard-compliant cutoff-shifted optical fibers are already installed. The combination of high throughput, reduced complexity, and compatibility with existing infrastructure points to a more scalable and energy-efficient future for optical communications.
This achievement was reported as a post deadline paper at the 51st European Conference on Optical Communication (ECOC) 2025 on Thursday Oct. 2, 2025, at the Bella Center, Copenhagen, Denmark, and was partly supported by the Japan-Germany Beyond 5G/6G collaboration initiative.

Background

Figure 1. Wavelength bands used in this work with single-mode E/S/C/L-bands and three-mode O-band.
New, data-driven internet services, including AI, have driven a surge in demand for optical fiber transmission bandwidth. Multi-band wavelength-division multiplexing (WDM) technology can significantly increase fiber capacity. This has been demonstrated in previous work using the O/E/S/C/L/U transmission bands, which utilize most of the available bandwidth in the low-loss region of optical fibers. However, without the availability of new spectral regions, the capacity of these systems is ultimately limited, necessitating the development of new fiber technologies to achieve even higher capacities.
In this demonstration, we surpassed previous limits by leveraging the fundamental physics of light transmission in specific types of standard-compliant optical fibers. We showed that the cutoff-shifted fibers defined in ITU-T G.654 recommendation can support multi-mode transmission when using O-band lightwaves, which have shorter wavelengths compared to the C and L bands that typically support only single-mode transmission. In these fibers, we were able to triple the capacity of the O-band. Combined with transmission in the E, S, C, and L bands—similar to our previous work—we achieved a record capacity of 430.2 Tb/s.

Achievements

Together with its partners, NICT developed the world’s first joint few- and single-mode transmission system capable of WDM transmission using commercially available standard G.654-compliant optical fiber.  The demonstration combined few-mode transmission in the O-band with single-mode transmission across the E/S/C/L-bands.
A wideband WDM signal was generated, comprising up to 209 spatial super-channels in the O-band and 706 channels across the E/S/C/L-bands, spanning a total bandwidth of 30.1 THz (1,280.4 nm to 1,608.9 nm) as shown in Figure 1. This signal was transmitted over 10 km of ITU-T G.654-B/D-compatible fiber. High data rates were achieved using dual-polarization quadrature amplitude modulation (DP-QAM) with up to 256 symbols per constellation. The generalized mutual information (GMI)-based estimated data rate after 10 km transmission reached 430.2 Tb/s. This surpasses the previously reported highest data rate in single-mode fiber (SMF), despite the aggregate transmission bandwidth (30.1 THz) being nearly 20% lower. Table 1 compares this result with our past achievements in wideband transmission experiments based on single-mode optical fiber transmission. These findings demonstrate that spatial division multiplexing can unlock untapped transmission resources in standard-compliant optical fibers.

Table 1. Comparison of wideband transmission demonstrations.


 
Transmission Capacity (Tb/s)
 Wavelength Count Total Bandwidth(THz)
O-band E-band S-band C-band L-band U-band Total
March 2022 256 - - 317 215 261 - 793 19.6
October 2023 321 - 315 315 200 267 - 1097 27.8
March 2024 402.2 302 314 318 195 253 123 1505 37.6
This result 430.2 209 199 225 141 141 - 915 30.1
 
New optical fiber technologies for ultra-high capacity are essential to support communication systems beyond 5G. To reduce adoption costs and implementation time, these technologies should be compatible with existing fiber infrastructure. Leveraging current networks enables faster deployment, improved efficiency, and reliable high-speed data transmission for future digital communication systems. The paper containing these results was presented at the post deadline session of the 51st European Conference on Optical Communication (ECOC) 2025, having been selected as a post deadline paper.

Future Prospects

NICT will continue to promote research and development into new technologies, components, and fibers to support new transmission windows for both near and long-term applications. NICT will also aim to extend the transmission range of such wideband, ultra-high-capacity systems and their compatibility for field deployed fibers.

Reference

European Conference on Optical Communication (ECOC) 2025, Post Deadline Session
Title: 430 Tb/s GMI data rate over a standard G.654 fiber using few-mode O-band and single-mode ESCL-band transmission
Authors: Ruben. S. Luis, Daniele Orsuti, Robert Emmerich, Aleksandr Donodin, Menno van den Hout, Stefano Gaiani, Besma Kalla, Lucas Zischler, Robson A. Colares, Julian Schneck, Shin Sato, Yuki Kawaguchi, Takemi Hasegawa, Tetsuya Hayashi, Simon Gross, Mark Bakovic, Michael Withford, Nicolas K. Fontaine, Mikael Mazur, Lauren Dallachiesa, Haoshuo Chen, Georg Rademacher, Roland Ryf, David Neilson, David A. Mello, Cristian Antonelli, Sergey Turitsyn, Tom Bradley, Pierpaolo Boffi, Chigo Okonkwo, Ronald Freund, Colja Schubert, and Hideaki Furukawa

Previous NICT Press Releases

Appendix

1. Newly developed transmission system

Figure 5 shows a schematic diagram of the newly developed transmission system.
① Lightwave comprising a total of 706 wavelength channels in the ESCL bands, and 209 wavelength 3-mode, O-band, spatial super channels, all originating from tunable lasers and shaped amplified spontaneous emission noise as dummy channels.
② Dual-polarization - 256-QAM, 64-QAM, 16-QAM or QPSK modulation is applied to multi-wavelength light with path delays for neighboring channels to emulate independent data-streams.
③ The optical signal is amplified by optical amplifiers in the O, E, S, C, and L bands, and combined by a multiplexer
④ Transmission over 10 km of standard G.654 fiber.
⑤ After propagation, the optical signal series in each wavelength band is separated by a demultiplexer, and the transmission loss is compensated by optical amplifiers for O, E, S, C, and L bands. 
⑥ Each optical signal is received on an offline coherent receiver, and the transmission performance is evaluated. The O-band spatial super channels use 3 receivers in parallel to recover the signals.
Figure 5. Schematic diagram of the transmission system using single-mode E+S+C+L-band signals and 3-mode O-band signals. We used Praseodymium, Bismuth, Thulium and Erbium-doped fiber amplifiers. The top shows infrared photos of the light at the fiber output. For long wavelengths, we only have the main mode (single-mode). For short wavelengths, we have the main mode and the higher order mode (multi-mode).

2. Results of experiment

In the experimental system shown in Figure 5, the transmission capacity (data rate) of the system was estimated by studying the received data-sequence and assuming the presence of the optimum error correction code (GMI estimated) data-rate. The graph of the experimental results in Figure 6 shows the GMI estimated data rate for each received channel. For most wavelengths, data rates of more than 400 Gb/s were obtained, with the highest data-rates observed in the C-band for the single-mode signals. The multi-mode signals achieved up to 900 Gb/s. A theoretical maximum data-rate of 430 Tb/s were achieved.
Figure 6. Summary of the achievable data rate for each of the transmitted bands. The total data rate was above 430 Tb/s.

Glossary

International Research Partners
This work is the result of an extensive international collaboration between NICT (Japan), Fraunhofer Heinrich-Hertz-Institut (Germany), Aston University (UK), Eindhoven University of Technology (Netherlands), Politecnico di Milano and University of L’Aquila (Italy), University of Campinas (Brazil), University of Stuttgart (Germany), Sumitomo Electric Industries Ltd. (Japan), Macquarie University and Modular Photonics (Australia), and Nokia Bell Labs (USA).
Terabit
One terabit is one trillion (1012) bits.
Standard-compliant cutoff-shifted optical fibers based on the ITU-T G.654 recommendation
The International Telecommunications Union (ITU) - Transport Standard G.654 Optical Fiber (ITU-T.G.654 standard optical fiber) was initially introduced in 1997 to specify low-loss fibers for submarine transmission. These fibers are especially designed with ultra-low loss and high effective area, in order to support very long distance transmission (trans-Atlantic and even trans-Pacific) and high powers. Since 2016, a variant of the standard was introduced to support terrestrial optical fiber networks. The high quality of terrestrial G.654 fibers has led to a surge in popularity with many deployments in regional, metropolitan and inter-datacenter networks. Unlike the more conventional standard fibers, G.654 fibers have larger core diameter. For this reason, they are often referred to as cut-off shifted single-mode optical fibers.
Transmission bands (OESCL) / Wavelength bands (Optical fiber transmission windows)
Various wavelength bands for optical fiber transmission, as summarized in Figure 2, are distinguished by regions with different transmission characteristics arising from physical properties of the fiber and amplifier technology. The C-band (wavelength 1,530 - 1,565 nm) and L-band (1,565 - 1,625 nm) are most commonly used for long-haul commercial transmission, with O-band (1,260 - 1,360 nm), used for short-range or inter data-center links. Recently, S-band (1,460 - 1,530 nm) transmission experiments have been enabled by development of Thulium (T-) doped fiber amplifiers (DFAs) and Bismuth (B-) and Praseodymium (P-) DFAs have been developed for O-band and E-band (1,360 - 1,460 nm). In this experiment we use P/B/TDFAs for O/E/S-bands, and Erbium (E-)DFAs for C/L-bands.
Figure 2. Optical communications wavelength bands.
Three-mode / Multi-mode Transmission
Figure 3. Single- and three-mode propagation in optical fibers. Single-mode longer wavelength signal can only propagate in a single-mode but a shorter wavelength signal can propagate in three-modes.
Optical fibers for long distance transmission are often referred to as “single-mode fibers”. As shown in Figure 3, these fibers have a core diameter that is similar to the wavelength of the light that is transmitted. So a single propagation mode is supported. However, if the wavelength of the light is much shorter than the core radius, higher propagation modes such as three-modes can be supported. In standard G.654 fibers, the threshold between single-mode and multi-mode transmission is just below the C-band, at 1,530 nm. This means that wavelengths below the 1,530 nm threshold can transmit with multiple modes whereas above 1,530 nm only single-mode is supported. In practice, multi-mode requires wavelengths significantly below the threshold. For this reason, we use O-band wavelengths, around 1,310 nm, more than 200 nm below the threshold, to use three-modes.
Multi-band wavelength division multiplexing (WDM) technology
Wavelength division multiplexing (WDM) is a method of transmitting optical signals of different wavelengths within a single optical fiber. WDM is a widely used technology to increase the transmission capacity in proportion to the number of wavelengths. In current optical fiber transmission systems, typically only C-band and occasionally L-band wavelengths are used. Wavelength bands such as T-band, O-band, E-band, S-band, and U-band have not yet been commercialized but are currently under research in labs around the world. Large WDM systems using many bands are often called Multi-band WDM systems.
Quadrature-amplitude modulation (QAM) 
QAM is a technique for modulating information data on optical signals using multiple levels of both phase and amplitude of the optical wave, that can enable very high spectral information density. 256-QAM uses 256 different signal symbols and can therefore encode 8 bits of information (28 = 256 bits) in each symbol. The spectral density of 256-QAM is therefore 8 times higher than for simple modulation formats such as on-off keying. 64-QAM symbols can encode 6 bits in 64 levels while 16-QAM symbols code 4 bits in 16 symbol sets. QAM symbols may also be transmitted in both polarizations simultaneously, increasing the number of bits transmitted in each dual polarization (DP) symbol to 16, 12 or 8 for DP-256QAM, DP-64QAM and DP-16QAM respectively. 
Past achievements in wideband transmission experiments
Figure 4 shows previous wideband, high data-rate (>200 Tb/s) transmission experiments based on single-mode optical fiber transmission. Previous NICT contributions are highlighted. The previous record was a 2024 Optical Fiber Communications (OFC) paper where a data rate of 402 Tb/s was achieved over a 37.5 THz bandwidth.
Figure 4. Recent data rate records and transmission bandwidths. This work achieved a higher data-rate with nearly 20% bandwidth reduction with respect to the last record.

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