Symmetric supermodes in cyclic multicore fibers

TL;DR

This paper analyzes symmetric supermodes in cyclic multicore fibers using symmetry principles, accounting for all inter-core couplings, and supports findings with finite-element simulations, aiming to improve telecommunications and sensing accuracy.

Contribution

It introduces a symmetry-based approach to accurately determine supermodes in cyclic multicore fibers, including high-order couplings, extending beyond traditional coupled-mode theory.

Findings

Only two modes involve all cores with opposite-phase configurations.

Results agree well with finite-element simulations.

Modes persist even as external cores form a continuous ring.

Abstract

Nearest-neighbor coupled-mode theory is a powerful framework to describe electromagnetic-wave propagation in multicore fibers but it lacks precision as the separation between cores decreases. We use abstract symmetries to study a ring of evenly distributed identical cores around a central core, a common configuration used in telecommunications and sensing. We find its normal modes and their effective propagation constants while including the effect of all high-order inter-core couplings. Finite-element simulations support our results to good agreement. Only two of these effective modes involve fields in all the cores. These two modes display opposite-sign phase configurations between the fields in the external cores and the central core. These two modes still appear in the limit where the external cores become a continuous ring. Our results might help improve predictions for crosstalk in telecommunications or precision in sensing applications.