Researchers from Japan’s National Institute of Information and Communication Technology (NICT) have achieved an astounding new Internet speed record of 319 Terabits per second (Tbps) over 3,001km.
The new speed is almost double the NICT’s own previous record speed of 178Tbps, which it recorded last year.
The NICT team and other researchers have been experimenting with a combination of advanced fibre technologies based on space-division multiplexing (SDM) to increase the capacity of optical data transmissions on fibre networks.
While fibre is an essential medium for fast and reliable data transfer in telecommunications, it is subject to fibre attenuation caused by a combination of natural characteristics such as material absorption, Rayleigh scattering, and Mie scattering.
To compensate for this, telecommunications infrastructure providers use amplification systems along the transmission line to improve signal strength.
For long-distance communication like on submarine cables that connect continents, this can be costly, which is why only the C and L-bands of the light spectrum are used.
These bands have longer wavelengths, which means they can carry data over longer distances with less loss. However, this combination currently limits the data rate to about 172Tbps over 2,040km.
The O-band, E-band, and S-band with shorter wavelengths are typically used for short-range communications.
The researchers have developed a four-core fibre optic cable that can exploit wider transmission bandwidth across the S, C, and L-bands.
Aside from having a larger number of cores than the typical fibre optic cable, the cladding around the cores measures 125µm, the same as on standard single-mode fibres, which ensures they are compatible with conventional cabling infrastructure.
This also eliminates the concerns related to the mechanical reliability of larger fibres.
To enable long-distance transmission using S-band signals, NICT constructed an experimental recirculating transmission loop that combined two kinds of rare-earth-doped fibre amplifiers with Raman amplification.
This was distributed along the transmission fibre to boost the signal.
The schematic below illustrates the make-up of the transmission system used for testing.
The researchers explained the system exploited wavelength division multiplexing (WDM) and a combination of optical amplification technology to enable long-haul transmission of 552 WDM channels from 1487.8 nm to 1608.33 nm.
“The system was used to measure achievable transmission throughput with each channel modulated with PDM-16QAM modulation at distances up to 3,001 km, where a data rate of 319 terabits per second was achieved,” the NICT said.
To compare this speed to other achievements in SDM fibres and transmission regimes, one can calculate and compare the product of transmission capacity and distance of the different solutions.
“The data rate times distance product becomes 957 petabits per second times km, which is over 2.7 times larger than previous demonstrations in SDM fibres with standard outer diameter,” the researchers said.
The graph below shows how the speed compares to what has been achieved using other fibre technologies.
The paper containing the results of the NICT’s experiment was published at the International Conference on Optical Fiber Communication held in early June.
“It was highly evaluated and was presented in the Post Deadline session, known for releasing the latest important research achievements,” the researchers stated.
The table below compares the number of cores, different technologies, and performance metrics of the different combinations of technologies with the latest solution developed by the NICT.