NEC, OCC and Sumitomo Electric complete subsea cable multicore fibre trial

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NEC Corporation (NEC), its subsidiary OCC Corporation and Sumitomo Electric Industries, (Sumitomo Electric) have completed the first trial of uncoupled 4-core submarine fibre cable.

The successful trial verified the transmission of the of uncoupled fibre performance to meet the demands of global telecoms networks. In coupled multicore fibres, the optical signals transmitting in the respective cores tend to interfere with each other, requiring special signal processing at the optical receiver. While uncoupled multicore fibres minimise the interference between the cores, meaning conventional (lower complexity) transmitters/receivers can be used.

Specifically, conventional single mode fibre has a single core within an individual fibre, while each multicore fibre contains multiple cores (4 cores in this case). This represents a four-fold enlargement in the number of spatial channels for the same amount of optical fibres and with the same fibre structure.


The uncoupled 4-core fibre is being deployed within the OCC SC500 series Lightweight cable, which has a 17mm outer diameter and withstands 8,000m water depth and can accommodate up to 32 fibres. With multicore fibre, the number of cores can be increased without increasing the cable diameter, with corresponding benefits in the cost per bit of the cable system.

To meet growing data demands, subsea networks are adopting space division multiplexing (SDM) technology, where the number of independent spatial channels is increased to maximise total system capacity, reduce power consumption and optimise cost per bit. Multicore fibre will further increase the number of parallel optical fibre cores without increasing the subsea cable size and structure, enabling the second generation of submarine SDM systems.


Through the trial, NEC and OCC demonstrated that the cable's optical transmission performance in the water meets the requirements of modern long-haul subsea cables. In addition, it showed that the process of cabling Sumitomo Electric's multicore fibre has no effect on its optical characteristics, achieving 'excellent' attenuation properties.