A multicore fiber (MCF) with the standard cladding diameter is expected to be deployed in the early stage of a spatial division multiplexing-based transmission system. Inter-core crosstalk in an MCF is closely related to the bending conditions, so it is expected to vary with the deployment conditions. The bending radius dependence of the crosstalk can be modeled in accordance with the power coupling theory. In this paper, we experimentally investigate the crosstalk property variation among spooled, cabled, and installed MCFs and show that the crosstalk increases slightly in the cabled and installed conditions compared to in the spooled fiber. We numerically examine this crosstalk change by considering the power coupling theory and actual bending conditions in a high-density optical cable. Our findings reveal that the crosstalk change during the cabling and installation processes corresponds to a change in the bending state, and that the crosstalk after installation has a good correlation with the effective bending radius in the cable.
A 3-mode fiber with pure silica core and dual-step index profile is numerically investigated for realizing low DMD and low loss. We found a structure that minimizes DMD while maintaining the low loss property of the pure silica core. We also show that lower loss and larger MFD properties are restricted by the requirement for the micro-bending sensitivity.
In order to construct 5G and beyond 5G networks effectively, it becomes important to prepare a sufficient number of interfaces with optical fiber at arbitrary locations. An optical wavelength- and power-tapping device is expected to provide a flexible junction point in optical networking, and a fiber-based optical device has great advantages in terms of low-loss and high compatibility with existing single-mode fibers. In this paper, we propose a wavelength- and powertunable in-fiber optical tap inscribed in a two-mode fiber (2MF) using a femtosecond laser. This optical tap is composed of a long-period fiber grating (LPG) and an asymmetric tap waveguide that is inserted transversely across the core to the cladding. In the LPG, transmitted LP01-mode light is converted into LP11 mode, and the converted LP11 mode is coupled to the tap waveguide while the LP01 mode passes through the fiber core. The operation wavelength and branching-power ratio can be controlled by the LPG design. We have revealed the optimum design for the tap waveguide. Here, the relationship among diameters of core and tap, the relative refractive indices of core and tap, and the angle between fiber core and tap was considered. We also experimentally confirmed the coupling efficiency to the core and tap when LP01 and LP11 modes were separately launched by using a tap waveguide inscribed in a 2MF. The factors that degraded the coupling efficiency were discussed by comparison with the calculation results.
KEYWORDS: Standards development, Single mode fibers, Cladding, L band, Space division multiplexing, Signal processing, Optical fiber cables, Interfaces, Connectors
We numerically show the applicability of standard 125 μm-cladding multi-core fiber (MCF) to long-haul and wide-band transmission in the S+C+L band. Although expanding the single-mode bandwidth is an effective way to increase the transmission capacity, the shortened cut-off wavelength degrades the XT and the Aeff. We numerically determine the optimum design of a four-core fiber with W-shape index profile considering the tradeoff relationship among the cut-off wavelength, Aeff, and XT. We show the design and applicability of a standard 125 μm-cladding MCF for S+C+L band transmission over long-haul distance of 1000 km and above with larger Aeff is possible from conventional single-mode fiber.
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