Researchers in Japan used the fourth core in 3000km long cable with standard 0.125mm cladding along with transmission in the S-band for the first time with 552 separate channels using wavelength division multiplexing (WDM)
The team at the National Institute of Information and Communications Technology (NICT) led by Benjamin Puttnam, constructed a transmission system that makes full use of wavelength division multiplexing from 1487.8nm to 1608.33nm by combining different amplifier technologies and the S (short) band at 1460nm to 1530nm. The C (conventional) band with erbium-boped amplifiers runs from 1530nm to 1565nm while the L (long) band runs from 1565nm to 1625nm.
Using a common comparison metric of optical fibre transmission the data-rate and distance produce of 957 petabits per second x km, is a world record for optical fibres with standard outer diameter.
The 120nm transmission bandwidth allowed 552 wavelength-division multiplexed channels by adopting two types of doped-fibre amplifier together with distributed Raman amplification, to enable recirculating transmission of the wideband signal. The standard cladding diameter, 4-core optical fibre can be cabled with existing equipment, boosting data rates in the near term, particularly for the backbone of 5G networks, rather than having to use new equipment.
The ability to deliver all these channel over a cable with four cores and standard cladding is key, as reducing the cladding diameter limits the number of spatial channels, leading to increasing interest in combining such fibres with wider transmission bandwidths in order to meet the expected growth in transmission capacity expected in SDM fibres.
Until now, NICT has built various transmission systems that make use of wavelength division multiplexing across the C and L-bands with modulation technology, but research in the S-band has transmission distance has been limited to only a few tens of kilometres.
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