Researchers from Japan’s National Institute of Information and Communications Technology have set a new internet speed record over a fiber optic connection. The researchers achieved a long-distance transmission of 319Tbit/s.
The previous world record of 178Tbit/s was set by British and Japanese researchers last year, but has been nearly doubled by NICT employees from Japan. Researchers used an optical fiber cable with four cores and a diameter of 0.125 mm. This achieved a speed of 319Tbit/s with a transmission bandwidth of more than 120nm.
The system uses, among other things, wavelength division multiplexing. This is a process of combining multiple optical channels on a single fiber optic cable. This is achieved by using different wavelengths. In addition, NICT used a combination of optical amplification technologies to enable long-distance transmission with 552 such WDM channels. Each channel had a wavelength between 1487.8nm and 1608.33nm. The channels also all used pdm-16qam modulation.
Wavelengths of the different optical bands. Source: NICT
Researchers used the optical S, C and L bands for the experiment. The former band is not normally used for long-distance transmissions, but this was made possible by signal amplification in an ‘experimental setup’, where small amounts of the rare thulium and erbium metals were added to the material of the fiber optic cable used. At certain wavelengths this could have a signal amplifying effect. Raman amplification was also used.
The researchers who set a record of 178Tbit/s last year also used the S-band, although that was over a distance of only 40 kilometers. NICT’s 319Tbit/s record was achieved over a significantly longer distance of 3001 kilometers. The researchers say they did not measure any signal loss or speed delays over that distance. According to NICT, a regular fiber optic infrastructure can in theory also be compatible with the technologies used, although this would first require adjustments on such a network.