NEC Corporation, OCC Corporation and Sumitomo
Electric Industries, Ltd. complete first trial ofsubmarine cable with multicore fiber
Submarine cables to feature a 4-fold increase in the number of
independent data channels with the next generation of space divisionmultiplexing (SDM) technology
Tokyo, October 4, 2021, NEC Corporation (NEC; TSE: 6701), its
subsidiary OCC Corporation and Sumitomo Electric Industries, Ltd.
(Sumitomo Electric; TSE: 5802) announced today that they havecompleted the first trial of uncoupled (*1) 4-core submarine fiber cable(*2), and verified its transmission performance to meet the exactingdemands of global telecommunications networks.
International data usage is expected to expand by 30-40% CAGR from2020-2026 (*3), driven by factors such as the growth of 5G mobile
data, and the need to share ever more content between data centers
distributed around the world. To meet this demand, submarine
networks are adopting space division multiplexing (SDM) technology,
where the number of independent spatial channels is increased tomaximize total system capacity, reduce power consumption andoptimize cost per bit. Multicore fiber is now expected to further increase
the number of parallel optical fiber cores without increasing thesubmarine cable size and structure, enabling the second generation ofsubmarine SDM systems.

Comparison of conventional and multicore fiber cables

Multicore fiber submarine cable features
Conventional single mode fiber has a single core within an individual
fiber. In contrast, each multicore fiber contains multiple cores (4 coresin this case). This represents a four-fold enlargement in the number ofspatial channels for the same amount of optical fibers and with thesame fiber structure: each fiber being 250µm diameter (0.25mm) aftercoating.
The uncoupled 4-core fiber is being deployed within the OCC SC500
series LW (Lightweight) cable, which has a 17mm outer diameter andwithstands 8,000 meter water depth. This cable can accommodate up
to 32 fibers. With multicore fiber, the number of cores can be increased
without increasing the cable diameter, with corresponding benefits inthe cost per bit of the cable system.

Image of OCC SC500 LW cable
Transmission performance demonstration
NEC and OCC have demonstrated that the cable’s optical transmission
performance in the water fully meets the exacting requirements ofmodern long-haul submarine cables. They further showed that theprocess of cabling Sumitomo Electric’s multicore fiber has no effect on
its optical characteristics, achieving excellent attenuation properties.
This research was supported by the Ministry of Internal Affairs andCommunications (MIC), Japan, under the initiative "Research andDevelopment of Innovative Optical Network Technology for a NovelSocial Infrastructure" (JPMI00316).

Notes:(*1) Uncoupled multicore fiber
Multicore fiber cables can be broadly divided into uncoupled and coupled multicore fibers. In
coupled multicore fibers, the optical signals propagating in the respective cores tend tointerfere with each other, requiring special signal processing at the optical receiver. In contrast,
uncoupled multicore fibers minimize the interference between the cores, allowing conventional(lower complexity) transmitters/receivers to be used.
(*2) Source: NEC Corporation, OCC Corporation and Sumitomo Electric Industries, Ltd.
research(*3) Source: Telegeography