Abstract
Wepropose a design for coupled-core multi-core fibers that allows to achieve extremely low levels of modal dispersion. These fibers, which we dub <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NEar-zero MOdal-dispersion</i> (NEMO) fibers, have an even number of cores regularly distributed on a circle, and the optimal design parameters follow from a simple condition independent of the number of cores. The modal-dispersion reduction trades off some of the fiber mode-mixing effectiveness, yet without compromising its beneficial property of mitigating nonlinear signal distortions. The semi-analytical tool developed for this study allows to effectively characterize the effect of various types of perturbations to the ideal fiber structure.
Highlights
Multi-core fibers (MCFs) for Space-Division Multiplexed (SDM) transmission allow simultaneous signaling in multiple spatial channels, and, depending on the inter-core distance, the extraction of the transmitted information may or may not require resorting to multiple-input multiple-output (MIMO) digital signal processing (DSP) techniques at the receiver
This reduction is of paramount importance, as modal dispersion (MD) is responsible for aggravating the MIMODSP complexity in the process of extracting the transmitted
We show that random coupling in NEar-zero MOdal-dispersion (NEMO) fibers occurs on the scale of hundreds of meters to a kilometer, longer than in homogeneous MCFs, but still sufficiently short to mitigate nonlinear distortions
Summary
Multi-core fibers (MCFs) for Space-Division Multiplexed (SDM) transmission allow simultaneous signaling in multiple spatial channels, and, depending on the inter-core distance, the extraction of the transmitted information may or may not require resorting to multiple-input multiple-output (MIMO) digital signal processing (DSP) techniques at the receiver. An important point that should be stressed is that the regime of strong mode mixing is achieved for a suitable fiber design, by properly balancing the various fiber parameters, which include the distance between the cores, their sizes, and their refractive index profiles (which results in changing the cores’ propagation constants). Within the range of parameters for which the fields in the fiber cores evolve in the regime of random mixing, there is room for optimizing the fiber design with the goal of reducing MD While this optimization is key to deploy practical CCMCF transmission, all reported studies, to the best of the authors’ knowledge, are limited to considering only the effect of varying the distance between homogeneous cores [10], [13]–[16]. We show that random coupling in NEMO fibers occurs on the scale of hundreds of meters to a kilometer, longer than in homogeneous MCFs, but still sufficiently short to mitigate nonlinear distortions
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