HTML5 Webook

59/64

NICT REPORT 57Research HighlightsPeta-b/s have been achieved by using hybrid of multimode/multicore fibers. However, such fibers were required to have much larger cladding diameter than standard single-mode fiber. To achieve practical implementation, the fiber cladding diameter must be re-duced to less than 0.2mm to ensure the necessary reliability standards, mainly regarding mechanical strength.NICT Network System Research In-stitute (NSRI), Fujikura Ltd. (Fujikura, President: Masahiko Ito) , Hokkaido Univ. (President: Toyoharu Nawa), and Macquarie Univ. MQ Photonics Re-search Centre (MQ)developed a three-mode four-core optical fiber, capable of wide-band wavelength multiplexing transmission with 0.16 mm cladding di-ameter (coating diameter: 0.25 mm) that can be easily cabled with existing equipment. They have successfully demonstrated a transmission experi-ment with a data-rate of 1.2 Peta-b/s. This is the world record throughput with an optical fiber with a cladding diameter below 0.2mm.Thinner fibers have several advan-tages such as volume productivity from same size of preform, less failure prob-ability and loss in fusion splicing, in addition to mechanical strength. Also, the core number of four has an ainity to data center communications.In order to achieve the transmission capacity of 1.2 Peta-b/s, mode and core multiplexing in a single optical coupler was used in combination with 256-QAM (quadrature-amplitude mod-ulation), which is a high-end practical high-density multilevel modulation op-tical signal, for a total of 368 wave-lengths. Digital MIMO (multiple-input and multiple-output) enabled un-scrambling the mixed modal signals for each individual core. This showed that multimode/multicore fiber which have compatible diameter with SMF can provide Peta-b/s transmission capabil-ity.Yoshinari Awaji and Hideaki Furuka-wa, both Research manager of the NSRI Photonic Network System Labo-ratory have stated: “We succeeded in Peta-b/s transmission with much thin-ner fiber than before. When laying of standard outer diameter optical fibers takes place, the existing equipment for cabling can be used and the practical use at an early stage is promising. "This is promis-ing for commer-cialization inter/intra-data center applications"Such kind of transmission system can be applied to inter-/intra- data center applications earlier, then the transmis-sion distance will be extended toward metro-area applications in the future if combined with brand-new fiber fabri-cation technology, which is researched by NICT through Industry-University-Government Cooperation.” The demonstration shows that SMF-compatible-diameter multimode/multi-core fibers can increase the capacity potential for eight times within same cable accommodation space. They say, “We will continue to research and de-velop future optical communication in-frastructure technologies which can smoothly accommodate traic such as big data and 5G services and beyond.”Fig. : Comparison of 3-mode/4-core fiber with previous fibersReferenceRuben S. Luís, Georg Rademacher, Benjamin J. Puttnam, Tobias A. Eriksson, Hideaki Furu-kawa, Andrew Ross-Adams, Simon Gross, Mi-chael Withford, Nicolas Riesen, Yusuke Sasaki, Kunimasa Saitoh, Kazuhiko Aikawa, Yoshinari Awaji, and Naoya Wada, “1.2 Pb/s Transmis-sion Over a 160 µm Cladding, 4-Core, 3-Mode Fiber, Using 368 C+L band PDM-256-QAM Channels,” in Proc. 44th European Conference on Optical Communication (ECOC), September 2018, paper Th3B.3.