Multicore fiber design housing a fluorine-doped low-latency core and cutoff shifted cores

Design of heterogeneous 4-core fiber housing a low-latency core and conventional cutoff shifted cores in a standard 125-μm cladding diameter is investigated to enable signal processing delay reduction using common mode impairment. For the low-latency core, 1-μs propagation delay reduction and an optical signal-to-noise ratio (OSNR) comparable to or greater than that of cutoff shifted cores are required. In this paper, we consider an F-doped core and depressed cladding structure with a large effective area as the low-latency core. It can be expected to achieve sufficient group delay reduction of the low-latency core, the OSNR unification among heterogeneous cores, and low inter-core crosstalk in a standard 125-μm cladding diameter. Consequently, we revealed the optimized low-latency core achieving the group delay reduction of 1 μs and the OSNR as same level as the cutoff shifted cores as we expected. The designed heterogeneous 4-core fiber with the standard 125-μm cladding diameter suppressed the inter-core crosstalk to be low enough to support a 1,000-km long transmission. We expect the figure-of-merit (FoM) of the 4-core fiber to be as high as previously reported 4-core fibers, and the FoM improvement are found when the low latency core and cutoff shifted core are placed alternately thanks to the core heterogeneity.