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World Record: 450 Tb/s Transmission Over a Metropolitan Link Using Legacy Optical Fiber

June 1, 2026

National Institute of Information and Communications Technology

Highlights

  • A new world record for optical data transmission: 450 Tb/s over a metropolitan network.
  • The transmitted signal occupied 42.4 THz of bandwidth - the widest ever sent through an optical fiber.
  • The result was achieved over already-installed (legacy) optical fiber in London, UK, linking University College London to the Telehouse North data center.
The National Institute of Information and Communications Technology (NICT, President: OHNO Hideo, Ph.D.), together with 5 international research partners, has demonstrated a record-breaking 450 terabits per second (Tb/s) optical transmission - the first time such a rate has been achieved over a field-deployed legacy fiber. The link, in London, UK, connects University College London (UCL) to the Telehouse North data center. This work is part of a long-standing collaboration between NICT and UCL.
The team introduced new optical-amplifier technologies that support ultra-wideband signals. Conventional commercial systems use up to about 10 THz of bandwidth, covering the C- and L-bands. The new system uses the O-, E-, S-, C- and L-bands together, more than quadrupling the available bandwidth to a record 42.4 THz. The resulting data rate of 450 Tb/s surpasses the previous records of 402 Tb/s and 430 Tb/s, set in 2024 and 2025 over laboratory fibers. Unlike those earlier demonstrations, the new experiment used real, already-installed fibers from the UK National Dark Fibre Facility (NDFF). This is therefore the closest demonstration to date of how the full capacity of existing fiber infrastructure could be unlocked, paving the way for the next generation of networks needed to support AI services and beyond-5G mobile systems.
This achievement was reported as a postdeadline paper at the 2026 Optical Fiber Communication Conference (OFC2026) on Thursday, March 19, 2026, at the Los Angeles Convention Center, Los Angeles, California, USA.

Background

New services such as AI, self-driving vehicles and beyond-5G mobile communications are placing growing demands on telecommunication networks. To meet these needs, the technique known as multi-band wavelength-division multiplexing (WDM) has been developed to make use of the full capacity of today's optical fibers. In earlier work, we demonstrated transmission across the O-, E-, S-, C-, L- and U-bands, which together cover most of the low-loss region of an optical fiber. That demonstration, however, was carried out only under ideal laboratory conditions.
In this new experiment, we exceeded the previous bandwidth and data-rate limits using new amplifier technologies covering the O-, E-, S-, C- and L-bands. Crucially, the experiment was performed over a field-deployed fiber link, which has significantly higher loss than a laboratory fiber due to splices, connectors and previous fiber-cut repairs. The link, installed in London, UK, runs from the UCL campus to the Telehouse North data center as shown in Figure 1.
Figure 1. Simplified diagram of the transmission experiment

Achievements

Working with its partners, NICT developed an optical-fiber transmission system with the widest bandwidth ever reported, 42.4 THz, and used it to send a signal through a field-deployed fiber in London, UK. With a total throughput of 450 Tb/s, the signal sets a new capacity record for a standard optical fiber. The wideband WDM signal contained up to 1,273 individual wavelength channels across the O-, E-, S-, C- and L-bands, spanning 42.4 THz of bandwidth (1,264.0 nm to 1,617.8 nm) as shown in Table 1. The signal was sent over 39 km of fiber, most of it running underground, between the UCL campus and the Telehouse data center in London Docklands, and back again. High data rates were obtained 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 39 km transmission reached 450 Tb/s. This surpasses the previously reported highest data rate in single-mode fiber (SMF). Table 1 compares this result with our results of past wideband transmission experiments. These results show that multi-band wavelength-division multiplexing can unlock previously untapped capacity in standard optical fibers.

     Table 1. Comparison of wideband transmission demonstrations
New ultra-high-capacity optical-fiber technologies will be essential for communications beyond 5G. To keep deployment costs and timelines manageable, they need to be compatible with the fiber infrastructure that is already in the ground. Building on existing networks in this way enables faster rollout, better use of resources and reliable high-speed connectivity for tomorrow’s digital services. The paper containing these results was presented at the postdeadline session of the 2026 Optical Fiber Communication Conference (OFC2026) on Thursday, March 19, 2026, at the Los Angeles Convention Center, Los Angeles, California, USA.

Future Prospects

NICT will continue to drive research and development on new technologies, components and fibers that open up additional transmission windows, for both near- and long-term applications. NICT also aims to extend the reach of these wideband, ultra-high-capacity systems and to broaden their compatibility with field-deployed fibers.

Reference

Optical Fiber Communication Conference (OFC) 2026, Postdeadline Session
Title: 450 Tb/s GMI, 42.4 THz, OESCL-Band Transmission Over a Field-Deployed Fiber
Authors: Ruben S. Luis, Jiaqian Yang, Romulo Aparecido, Mindaugas Jarmolovicius, Eric Sillekens, Ronit Sohanpal, Zelin Gan, Aleksandr Donodin, Vitaly Mikhailov, Jiawei Luo, David DiGiovanni, Nicolas Fontaine, Lauren Dallachiesa, Mikael Mazur, Roland Ryf, Haoshuo Chen, David Neilson, Ian Phillips, Wladek Forysiak, Sergei Turitsyn, Daniele Orsuti, Hideaki Furukawa, Robert Killey, and Polina Bayvel.

Previous NICT Press Releases

Related Press Release

Appendix

1. Newly developed transmission system

Figure 2 shows a schematic diagram of the newly developed transmission system.
① A wideband signal made up of 1,273 wavelength channels covering the O-, E-, S-, C- and L-bands is generated using tunable lasers, together with shaped amplified spontaneous-emission noise that acts as additional dummy channels.
② Each channel is modulated using dual-polarization 256-QAM, 64-QAM, 16-QAM or QPSK, with small path delays added between neighboring channels so that they behave like 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 39 km of standard field-deployed 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.
Figure 2. Schematic diagram of the transmission system using O-, E-, S-, C- and L-band signals
The system uses bismuth-, thulium- and erbium-doped fiber amplifiers. The signal is generated at the UCL campus and sent over the NDFF fiber to the Telehouse data center, where it is looped back over a second fiber to UCL for reception and processing. The total achieved capacity was 450 Tb/s.

2. Results of experiment

For the experimental setup shown in Figure 2, the transmission capacity (data rate) was estimated from the received data sequence assuming the use of an optimal error-correction code (this is the so-called GMI-estimated data rate). Figure 3 shows the GMI-estimated data rate for each received channel. For most wavelengths, the achieved rate exceeded 400 Gb/s, with the highest rates observed in the C-band. The total combined data rate reached 450 Tb/s.
Figure 3. Achieved data rate for each of the 1,273 channels and combined throughput of each band
The colors indicate the selected modulation formats for each channel.

Glossary

International Research Partners This work is the result of an extensive international collaboration between NICT (Japan), University College London (UK), Aston University (UK), Lightera Laboratories (USA), Nokia Bell Labs (USA) and the University of Bristol (UK). Back to contents

Terabit
One terabit is one trillion (1012) bits. Back to contents

Transmission bands (OESCL) / Wavelength bands (Optical fiber transmission windows)

Figure 4. Optical communications wavelength bands

Various wavelength bands for optical fiber transmission, as summarized in Figure 4, are defined by regions with distinct transmission characteristics, set by the physical properties of the fiber and the available amplifier technology. The C-band (1,530 - 1,565 nm) and L-band (1,565 - 1,625 nm) are the most commonly used for long-haul commercial systems, while the O-band (1,260 - 1,360 nm) is typically used for short-range or inter-data-center links. More recently, S-band (1,460 - 1,530 nm) experiments have become possible thanks to thulium-doped fiber amplifiers (TDFAs), and bismuth-doped fiber amplifiers (BDFAs) have been developed for the O-band and E-band (1,360 - 1,460 nm). In this experiment we used BDFAs and TDFAs for the O-, E- and S-bands, and erbium-doped fiber amplifiers (EDFAs) for the C- and L-bands. Back to contents

Quadrature-amplitude modulation (QAM) QAM is a technique for encoding information onto an optical signal by varying both the phase and the amplitude of the light wave, allowing many bits of data to be packed into a single symbol. 4-QAM uses 4 different signal symbols to carry 2 bits of information per symbol, while 256-QAM uses 256 different symbols and can therefore carry 8 bits of information per symbol (28 = 256 symbols). The spectral efficiency of 256-QAM is therefore eight times higher than that of simple formats such as on-off keying. Similarly, 64-QAM carries 6 bits per symbol over 64 different signal levels, and 16-QAM carries 4 bits per symbol over 16 levels. QAM symbols can also be transmitted on both polarizations of the light at once, doubling the number of bits per symbol to 16, 12 or 8 for DP-256QAM, DP-64QAM and DP-16QAM respectively. Back to contents

Past achievements in wideband transmission experiments Figure 5 shows previous wideband, high data-rate (>200 Tb/s) transmission experiments performed in single-mode fibers; previous NICT contributions are highlighted. The previous record, set at the 2024 Optical Fiber Communication Conference (OFC), reached a data rate of 402 Tb/s over a 37.5 THz bandwidth. Back to contents

Figure 5. Recent data rate records and transmission bandwidths with laboratory and field-deployed fibers

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LUIS Ruben, FURUKAWA Hideaki
Photonic Network Laboratory
Photonic ICT Research Center
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