Tom's Hardware reports that Japan's National Institute of Information and Communications Technology (working with the Aston Institute of Photonic Technologies and Nokia Bell) set a 402 terabits per second data transfer record — over commercially available optical fiber cables.
The NICT and its partners were able to transmit signals through 1,505 channels over 50 km (about 31 miles) of optic fiber cable for this experiment. It used six types of amplifiers and an optical gain equalizer that taps into the unused 37 THz bandwidth to enable the 402 Tb/s transfer speed. One of the amplifiers this was demonstrated with is a thulium-based doped fiber amplifier, which uses C-band or C+L band systems. Additionally, semiconductor optical amplifiers and Raman amplifiers were used, which achieved 256 Tb/s data rate through almost 20 THz. Other amplifiers were also used for this exercise which provided a cumulative bandwidth of 25 THz for up to 119 Tb/s data rate.

As a result, its maximum achievable result surpassed the previous data rate capacity by over 25 percent and increased transmission bandwidth by 35 percent.

"This is achievable with currently available technology used by internet service providers..." the article points out.

"With 'beyond 5G' potential speeds achievable through commercially available cables, it will likely further a new generation of internet services."