NEC Corp. (TSE: 6701), its subsidiary OCC Corp., and Sumitomo Electric Industries, Ltd. (TSE: 5802) reported that they are the first to trial uncoupled four-core multicore submarine cable. Paired with space-division multiplexing (SDM) transmission, such multicore fiber could help meet future submarine network capacity requirements, the companies posit.
Multicore fiber can increase the number of parallel optical fiber cores in a system without increasing the submarine cable size and structure, say the companies. The uncoupled four-core fiber deployed in this case used the OCC SC500 series LW (lightweight) cable, which has a 17-mm outer diameter and is designed to operate at depths up to 8,000 m. The cable can accommodate up to 32 fibers – but four-core fiber would provide significant capacity expansion within such a fiber count, the companies point out.
NEC and OCC demonstrated that the cable's optical transmission performance in the water meets the performance requirements of modern long-haul submarine cables. They also demonstrated that the cabling of Sumitomo Electric's multicore fiber had no effect on its optical characteristics.
The companies point out that the use of uncoupled multicore fiber cables is a key component of future success for the technology. Optical signals propagating in the respective cores of coupled multicore fiber tend to interfere with each other, they say, and thus would require additional signal processing at the optical receiver. Uncoupled multicore fibers minimize the interference between the cores, which enables the use of conventional transmitters and receivers.
Japan’s Ministry of Internal Affairs and Communications (MIC) supported the demonstration as part of its "Research and Development of Innovative Optical Network Technology for a Novel Social Infrastructure" (JPMI00316) initiative.
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