DOI: 10.11648/j.ajset.20261104.34 ISSN: 2578-8353

Design and Numerical Modeling of a Concentric Dual-Core Optical Fiber with Hybrid Single-Mode and Multimode Propagation

Randriana Erica, Ando Andriamanalina
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This study presents a numerical investigation of an original dual-core optical fiber designed to simultaneously support single-mode propagation in one core and multimode propagation in the other. The proposed structure consists of two closely spaced guiding cores embedded within a common silica cladding. The geometrical dimensions and refractive-index parameters of the two cores are independently adjusted to establish distinct modal regimes within the same fiber. The main objective is to demonstrate the feasibility of this configuration and to analyze the influence of the main structural parameters on modal behavior, optical confinement, guided power distribution, and coupling between the two cores. The numerical analysis considers the core diameters, refractive-index contrasts, operating wavelength, and inter-core separation as the principal parameters governing light propagation. The normalized frequency of each core is evaluated to determine its propagation regime and the number of supported modes. Numerical simulations are then performed to characterize the guided modes, electromagnetic field distributions, guided power fractions, and inter-core power transfer. Particular attention is given to the spatial distribution of the optical field and to the interaction between the two guiding regions. The obtained results demonstrate that the proposed dual-core configuration can successfully maintain fundamental single-mode propagation in one core while simultaneously supporting several guided modes in the second core. The simulations also show that the modal characteristics and power distribution are strongly influenced by the dimensions of the cores, the refractive-index differences, and the distance separating the two cores. Variations in these parameters modify the confinement of the electromagnetic field and consequently affect the optical interaction and power exchange between the guiding regions. Appropriate selection of the geometrical and optical parameters therefore provides an effective means of controlling the propagation characteristics of the proposed fiber. These results confirm the numerical feasibility of integrating single-mode and multimode propagation within a single dual-core optical fiber. The proposed structure provides additional flexibility for controlling guided modes, optical confinement, and inter-core power transfer. It may therefore offer promising perspectives for high-capacity optical transmission, spatial mode multiplexing, coupling control, and advanced optical sensing applications. This study provides a numerical basis for the further optimization and experimental development of dual-core fiber structures combining distinct modal propagation regimes.

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