A team of researchers from Japan and the United Kingdom have achieved a record breaking data transmission speed through the commercial-grade fibre. By expanding fibre’s communication bandwidth, the team has produced data rates up to four times as fast as existing commercial systems—a 33 percent increase on the previous record.
The team, led by the Photonic Network Laboratory of the National Institute of Information and Communications Technology (NICT) demonstrated a record-breaking aggregate optical transmission bandwidth of 37.6 THz to enable a new data-rate record of 402 terabits per second in a standard commercially available optical fibre.
This record was achieved by constructing the first optical transmission system covering all the transmission bands (OESCLU) of the low-loss window of standard optical fibres. The system combined various amplification technologies, some developed for this demonstration, including 6 kinds of doped fibre optical amplifiers, and both discrete and distributed Raman amplification. Novel optical gain equalizers also allowed access to new wavelength bands that are not yet utilized in deployed systems. The newly developed technology is expected to make a significant contribution to expand the communication capacity of the optical communication infrastructure as future data services rapidly increase demand.
The results of this experiment were accepted as a post-deadline paper at the 47th International Conference on Optical fibre Communications (OFC 2024) and presented by Ben Puttnam on Thursday March 28, 2024 at the San Diego Convention Center, California, USA.
The growth of internet and data services has driven demand for optical transmission bandwidth. To meet this demand, multi-band wavelength division multiplexing (WDM) technology, where new spectral windows are used to increase optical fibre transmission bandwidth, has become a popular research topic. Utilising new transmission windows in deployed fibres also offers a potentially significant benefit in the near term as a method of extending the life of existing fibre systems to provide additional transmission capacity without the large capital expenditure associated with new fibre deployment.
However, moving away from the lowest loss regions of standard silica fibres requires new amplification schemes beyond the standard erbium (E-) doped fibre amplifier (DFA) that is a staple of C-band or C+L-band systems. Previously, S/C/L-band transmission has been explored with various amplifier solutions. In addition to thulium (T-) DFAs, semiconductor optical amplifiers (SOAs), distributed and discrete Raman amplification have been used, with maximum estimated data rates of 256 Tb/s utilising almost 20 THz bandwidth. Even wider transmission demonstrations have used bismuth (B-DFAs) for O-band and lumped Raman amplifiers for U-band channels for 119 Tb/s with a cumulative bandwidth of 25 THz.
Along with collaborating partners, NICT constructed the world’s first O to U-band transmission system capable of DWDM transmission in a commercially available standard optical fibre achieved with custom-designed amplifier technology. The transmission demonstration utilises 6 DFA variants for gain in O/E/S/C/L-bands with discrete (U-band) and distributed Raman amplification along with novel optical gain equalisers for profile shaping in O/E bands.
A wideband DWDM signal comprising up to 1,505 channels covering 275 nm (37.6 THz), from 1,281.2 nm to 1,649.9 nm, across the O, E, S, C, L and U-bands was transmitted over 50 km of water absorption peak suppressed optical fibre. High data rates were achieved by using dual polarisation (DP-)quadrature-amplitude modulation (QAM) with up to 256 symbols per constellation.
The generalised mutual information (GMI) estimated data rate after 50 km transmission was 402 Tb/s, which exceeds the previous highest single-mode fibre (SMF) data rate by over 25% and the aggregate transmission bandwidth of 37.6 THz is also a 35% increase. The achieved data rate is compared with past achievements in wideband transmission experiments in Figure 4. These results show the potential of ultra-wideband transmission, enabled by a new amplifier and wideband spectrum-shaping technology to increase the information-carrying capability of new and deployed optical fibers.
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 fibre networks to perform higher data-rate transmission and extend the useful life of existing network systems. It is also anticipated that new bands can address the increasing demand of next-generation communications services by combining with new types of optical fibres.
