New 22.9 Petabit Fibre Pair Record Using Multi-Core & Multi-Band

The Japanese National Institute of Information and Communication set a single fibre pair transmission record of 22.9 petabits last November. To achieve it, multicore was combined with multiple frequency bands including the standard C-band, L-band (in limited production use today), and S-band. The C-band is the work horse of optical infrared transmission with a wavelength range of 1530-1550 nanometers. These wavelengths experience the least attenuation in a glass medium; they are also ideal for erbium-doped optical amplifiers. The L-band includes the 1565 to 1625 nanometer range. Its attenuation in glass is the second lowest. Arelion has used L-band in its US East Coast network. At least one Pacific cable has used L-band as well. I believe it is PLNC which connects HK to the US. The S-band ranges from 1460 to 1515 nanometers. The 'S' stands for short band. It has the third lowest attenuation in glass.

The Japanese combined these three bands with a 38 core fibre strand which they shot over the relatively short distance of 13 kilometers. One challenge with multicore fibre (a core is simply the glass through which optical signals propagate) is cross talk due to their close proximity. Cross talk distort the light pulses and leads to high bit error rates. That is why this test was done over a 12 kilometer span. Anything longer and the BER would have been unacceptable for commercial transmission purposes. 




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