World Record 301 Tb/s Transmission in a Standard Commercially Available Optical Fiber

- Achieved by developing technologies that open up new wavelength regions for future optical communication infrastructure -

January 29, 2024
(Japanese version released on November 30, 2023)

National Institute of Information and Communications Technology
Nokia Bell Labs


  • Record data-rate of 301 Tb/s in a standard commercially available optical fiber
  • 27.8 THz optical bandwidth achieved by developing new optical amplifiers and optical gain equalizers for new wavelength (E) band
  • Significant contribution to the capacity expansion of optical communication infrastructure to meet the expected demand from new data-services
Researchers from the National Institute of Information and Communications Technology (NICT, President: TOKUDA Hideyuki, Ph.D.), in collaboration with Nokia Bell Labs, Aston University, and Amonics PLC, demonstrated a record-breaking data-rate of 301 terabits per second in a commercially available standard optical fiber.
This record was achieved by developing new optical amplifiers and optical gain equalizers to open up new wavelength bands that are not yet utilized in deployed systems. The newly developed technology is expected to make a significant contribution to expanding the communication capacity of the optical communication infrastructure as new data services rapidly increase demand.
The results of this experiment were accepted as a post-deadline paper at the European Conference on Optical Communication (ECOC) 2023 and presented by Ben Puttnam on Thursday October 5, 2023 at the Scottish Event Campus (SEC), Glasgow, UK.


Figure 1 Wavelength bands used in optical communications
To meet the demand for enhanced data services, multi-band wavelength division multiplexing (WDM) technology using additional spectral windows for optical fiber transmission has been widely investigated. Adopting new transmission windows offers a potentially significant benefit in the near-term as a method of extending the life of already deployed optical fibers to provide additional transmission capacity without the large capital expenditure associated with new fiber deployment. However, moving away from the low-loss window of standard single-mode fibers (SMFs) requires new devices and amplification schemes beyond the standard erbium-doped fiber amplifier (DFA) that is a staple of C or C/L-band systems. Previously, S/C/L-band transmission has been explored with various amplifier technologies supplementing erbium DFAs including semiconductor optical amplifiers, Raman amplification and thulium-DFAs. NICT previously showed that combining DFAs with distributed Raman amplification has enabled 244.3 Tb/s transmission covering 19.8 THz over 54 km of SMF and more than 1 Pb/s when using a 20 THz bandwidth signal in a 4-core fiber with standard cladding diameter. 
In this demonstration, we further expand dense wavelength division multiplexed (DWDM) transmission to include the E-band to enable more than 1,000 parallel (DWDM) transmission channels with 27.8 THz (212.3 nm) optical bandwidth.


Along with collaborating partners, NICT constructed the world’s first E to L-band transmission system capable of DWDM transmission in a commercially available standard optical fiber supported by the development of new bismuth-doped fiber amplifier (BDFAs) and multi-port E-band optical processors (OP) for gain equalization (Details shown in Figure 3). The BDFA was used along-side thulium- and erbium- doped fiber amplifiers (T/E-DFA) together with distributed Raman amplification. In addition to the BDFA, the experiment required use of a prototype E-band gain equalizer to shape the E-band transmission spectrum.

A wideband DWDM signal comprising up to 1,097 channels covering 212.3 nm (27.8 THz) from 1,410.8 nm to 1,623.1 nm over the E, S, C and L-bands was transmitted up to 150 km. High data-rates were achieved by using dual polarization (DP-)QAM utilized with up to 256 symbols per constellation. As highlighted in Table 1, the data-rate after 50 km transmission with implemented LDPC decoding was 301 Tb/s, which exceeds the previous highest single-mode fiber (SMF) data-rate by over 23% and the near continuous transmission bandwidth of 27.8 THz is also a 41% increase. The generalized mutual information (GMI) estimated data-rate of 321 Tb/s is compared with past achievements in wideband transmission experiments in Figure 4. These results show the potential of E-band transmission, enabled by a new BDFA and multi-port OP, to increase the information carrying capability of new and deployed optical fibers.
Table 1 Table comparing previous wideband transmission demonstration

It is expected that the data-rate of optical transmission systems required to enable Beyond 5G information services will increase enormously. New wavelength regions enable deployed optical fiber networks to perform higher data-rate transmission and extend the useful life of existing network systems. It is also hoped that new bands can address the increasing demand of next generation communications services by combining with new types of optical fibers.

The paper containing these results was presented at the European Conference on Optical Communication (ECOC) 2023, one of the largest international conferences related to optical communications, having been selected as a post-deadline paper. The post-deadline session is a special session at the end of the conference to showcase the latest important research achievements and was held on Thursday October 5 at the Scottish event campus (SEC) in Glasgow, UK.

Future Prospects

NICT will continue to promote research and development into new amplifier 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.


49th European Conference on Optical Communications (ECOC) 2023, Post Deadline Session
Title: 301 Tb/s E, S, C+L-Band Transmission over 212 nm bandwidth with E-band Bismuth-Doped Fiber Amplifier and Gain Equalizer
Authors: Benjamin. J. Puttnam, Ruben. S. Luis, Yetian Huang, Ian Phillips, Dicky Chung, Nicolas K. Fontaine, G. Rademacher, Mikael Mazur, Lauren Dallachiesa, Haoshuo Chen, Wladek Forysiak, Ray Man, Roland Ryf, David T. Neilson, and Hideaki Furukawa

Previous NICT press releases


1. Newly developed transmission system

Figure 5 Schematic diagram of the transmission system
Figure 5 shows a schematic diagram of the newly developed transmission system.
① Lightwave comprising a total of 1,097 wavelengths originating from tunable lasers and shaped amplified spontaneous emission noise as dummy channels.
② Dual-polarization - 256 QAM or 64 QAM 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 E, S, C, and L bands.
④ The transmission spectrum is shaped by dynamic gain equalizer that also allows combination of test and dummy channels.
⑤ Transmission over 50 km, 100 km or 150 km of single-mode fiber. To compensate for high transmission loss in E and S-bands, back propagating distributed Raman amplification is used with pump light added in WDM coupler after the fiber.
⑥ The optical signal series in each wavelength band is separated by a divider, received by each receiver, and the transmission error is measured.
⑦ After propagation, the transmission loss is compensated before reception by optical amplifiers in the E, S, C, and L bands.
⑧ Each core signal is received on offline coherent receiver, and the transmission performance is evaluated.

2. Results of this experiment

In the experimental system shown in Figure 5, the transmission capacity (data rate) of the system was estimated in 2 ways. Firstly by studying the received data-sequence and assuming the presence of the optimum error correction code (GMI estimated data-rate), and secondly, by directly applying error coding on the received bits.
The graph of the experimental results of Figure 6 shows the data rate for each wavelength after applying error correction decoding. For most wavelengths, data rates of more than 250 gigabits per second were obtained, with the highest data-rates observed in S-band. A total of 301 terabits per second were achieved for 1,097 wavelengths with total data-rate assuming an optimum code giving a theoretical maximum data-rate of 322 Tb/s.

Figure 6 Summary of achieved data-rate measurement


One terabit is one trillion (1012) bits. One gigabit is one billion (109) bits.

Figure 2 Profile of standard single-mode optical fiber

Standard optical fiber

According to international standards, the outer diameter of the glass (cladding) of optical fibers is 0.125 ± 0.0007 mm, and the outer diameter of the coating layer is 0.235 to 0.265 mm. The optical fiber widely used in optical communication systems is a single-core single-mode fiber with an outer diameter of 0.125 mm, and the capacity limit is considered to be about 100 terabits per second in the conventional C and L-bands.

Optical amplifier

Optical fibers have a very small transmission loss compared to coaxial and other electrical cables, but since data is often transmitted over long distances, it is necessary to compensate for attenuation periodically, typically after several tens of kilometers. This is usually done in an optical amplifier which may amplify many wavelength (WDM) channels simultaneously. A common practical amplification method uses rare-earth doped fibers. By adding a small amount of rare earth ions such as erbium/thulium ions or in the case of our new amplifier, bismuth and germanium to the base material of an optical fiber, amplification can be achieved by exciting these ions with lower wavelength pump lasers and then amplifying signal photons through stimulated emission. Such amplifiers have significantly increased the transmission range of optical fiber communication and allowed amplification of many wavelength channels simultaneously. For recent wide-band transmission systems other amplification schemes such as Raman amplification and semiconductor optical amplifiers, have been also employed.

Optical gain equalizer

Equipment that adjusts the relative intensity of light signals at different wavelengths. Among various technologies one approach for gain equalization uses an optical diffraction grating and a spatial light modulator. In this study, we developed an optical intensity adjuster that adjusts a large number of wavelengths in the E band within a single unit.

Wavelength bands (Optical fiber transmission windows)

Various wavelength bands for optical fiber transmission are defined, distinguished by regions with different transmission characteristics arising from physical properties of the fiber, as summarized in Figure 3. The C band (Conventional band, wavelength 1,530 - 1,565 nm) and L band (Long wavelength band, 1,565 - 1,625 nm) are most commonly used for longer commercial transmission, with O band (Original band, 1,260 - 1,360 nm), currently used only for short-range or inter data-centre communications. Although the T band (Thousand band, 1,000 - 1,260 nm), U band (Ultralong wavelength band, 1,625 - 1,675 nm) is rarely used due to lack of suitable amplification, new amplifier technologies have recently enabled research into the use of S band (Short wavelength band, 1,460 - 1,530 nm). In this experiment we utilize the E band (Extended band,1,360 - 1,460 nm), for the first time, combining with S, C and L-band for dense WDM transmission.

Figure 3 Optical communication wavelength band

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 the current optical fiber transmission system, typically only C-band and occasionally L-band wavelength are used. Wavelength bands such as T-band, E-band, S-band, and U-band have not yet been commercialized but currently under research in labs around the world. Large WDM systems using many bands are often called Multi-band WDM systems.

Raman amplification

Raman amplification is based on stimulated Raman scattering, when signal photons induce the inelastic scattering of a lower wavelength 'pump' photon in a non-linear optical medium. When this occurs, additional signal photons are produced, with the surplus energy resonantly passed to the vibrational states of molecules in the fiber core. This process, as with other stimulated emission processes, allows all-optical amplification in optical fibers with the gain depending on material of the fiber core.

Quadrature-amplitude modulation (QAM) - Dual polarization (DP)
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. 64QAM symbols can encode 6 bits in 64 levels while 16QAM 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.

Generalized mutual information (GMI)

Generalized mutual information is a measure amount of shared information between the transmitted and received signals and provides the number bits per symbol that can be successfully transmitted after decoding, assuming the presence of an optimal error correction code. The data-rate estimated from the GMI is and upper bound and typically higher than the data-rate obtained with the available error correcting codes implemented in real systems.

Past achievements

Figure 4 summarized previous wideband (>100nm), high data-rate (>100 Tb/s) transmission experiments in single-mode fibers. Previous contributions from NICT are also highlighted in red. The previous record was a 2022 journal paper submission using 157 nm over S, C and L-bands.
‘Benjamin J. Puttnam,, “S-, C- and L-band transmission over a 157 nm bandwidth using doped fiber and distributed Raman amplification”, Opt. Express, vol. 30, no. 6, p. 10011, Mar. 2022.’

Figure 4 Recent wideband experiments in single mode fiber

New type of optical fiber

An alternative method of increasing the transmission capacity of optical fibers is by utilizing the spatial domain to support multiple communications channels in the same fiber. This can be in multi-core fibers where many cores are supported in the same cladding or multi-mode fibers where an enlarged core supports many modes. Such fiber requires large changes to optical communications system design, particularly if the diameter of the fiber increases. Hence, even when designing systems with such fibers, it is advantageous to maximize the capacity of each spatial channel to increase data-rates whilst maintaining the same outer-diameter as standard optical fibers that are widely used for optical communications.

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