Researchers break optical data transmission record

A research group bringing together scientists from around the world has achieved a record by demonstrating an aggregate optical transmission bandwidth capable of operating at 37.6 THz and a data rate of 402 terabits per second over a standard commercially available optical fibre. The previous record was 321 Tbps set last year.

The work, led by the Photonic Network Laboratory of Japan’s National Institute of Information and Communications Technology (NICT), developed the first optical transmission system covering all the transmission bands (OESCLU) of the low-loss window of standard optical fibres. The system also combined various amplification technologies, some developed for this demonstration, including six types of doped optical fibre amplifiers and discrete and distributed Raman amplification. In addition, new optical gain equalisers allowed access to new wavelength bands not yet used in deployed systems. The newly developed technology is expected to contribute significantly to expanding the communication capacity of optical communication infrastructures.

The results of the experiment were accepted as a post-term paper at the 47th International Conference on Optical Fibre Communication (OFC 2024).

More details

The use of new transmission windows in fibres already deployed offers a potentially significant short-term benefit as a method of extending the life of existing fibre systems with additional transmission capacity without major capital investments associated with the deployment of new fibres.

However, moving away from the lower loss regions of standard silica fibres requires new amplification schemes in addition to the erbium doped fibre amplifier (DFA). Until now, S/C/L band transmission had been explored with various amplifier solutions. In addition to thulium (T-) DFAs, semiconductor optical amplifiers (SOAs), distributed and discrete Raman amplification were used, with estimated maximum data rates of 256 Tb/s using a bandwidth of almost 20 THz. Even more extensive transmission demonstrations used bismuth (B-DFAs) for O-band and concentrated Raman amplifiers for U-band channels for 119 Tb/s with a cumulative bandwidth of 25 THz. E-band B-DFAs were also used with distributed Raman amplification for E/S/C/L band transmission above 27.8 THz with an estimated data rate of less than 320 Tb/s.

In this demonstration, dense wavelength division multiplexed transmission was expanded to cover all the main transmission bands in the low loss window of standard optical fibres to enable more than 1,500 parallel transmission channels within an aggregate optical bandwidth of 37.6 THz.

Learning more about fibre optics

Optical fibres have very low losses during transmission compared to coaxial cables and other electrical models, but it is necessary to compensate for attenuation periodically in order to transmit over long distances. This is usually done by an optical amplifier, which can amplify several wavelength channels simultaneously.

A common amplification method uses fibres doped with rare elements. By adding a small amount of rare element ions, such as erbium, thulium or bismuth, to the basic material of optical fibres, amplification can be achieved by exciting these ions with shorter wavelength lasers.

Such amplifiers significantly increase the transmission range of fibres and allow the amplification of many wavelength channels simultaneously. Recent broadband transmission systems have also employed alternative amplifiers, such as Raman amplification and semiconductor optical amplifiers.