Researchers in Japan

Japan’s National Institute of Information and Communications Technology (NICT), in partnership with Fujikura, has demonstrated a transmission experiment over 1,045km with a data-rate of 159Tb/s. This was achieved using the recently developed three-mode optical fibre, which is capable of wide-band wavelength multiplexing transmission with standard outer diameter (0.125mm) that can be cabled with existing equipment.

The organisations believe this achievement shows that such limitations previously associated with multimode fibres can be overcome. It has historically, they said, been difficult to simultaneously satisfy large data-rates and long-distance transmission due to different propagation delays between optical signals in different modes.

NICT constructed the transmission system using an optical fibre developed by Fujikura, and successfully transmitted over 1,045km with a data-rate of 159Tb/s. Converting the results to the product of transmission data-rate and distance results in 166Pb/s×km, which NICT says is approximately twice the world record so far in the few-mode fibres and the largest data-rate over 1,000km for any kind of standard-diameter fibre.

The system includes the three-mode optical fibre; 348 wavelength optical comb light source; 16-quadrature amplitude modulation (QAM) multi-level modulation technology equivalent to four bits/single polarisation symbol; and separation technology of multimode optical signals with different propagation speeds in fibre, which enables unscrambling of mixed modal signals even after transmission over more than 1,000km. This demonstrates that standard outer diameter multimode fibres can be used for communication of high capacity optical backbone transmission systems.

In a statement, the NICT said: ‘When laying of standard outer diameter optical fibres takes place, the existing equipment can be used and the practical use at an early stage is promising. Also, ultimate large-capacity transmission will become possible in the future if combined with multicore technology, which is researched by NICT in cooperation with industry, university and government in Japan. We will continue to research and develop future optical communication infrastructure technologies which can smoothly accommodate traffic such as big data and 5G network services.’