Inter-Core Crosstalk In Dual-Core Optical Fibers: Mechanisms And Mitigation

Abstract

The rapid growth of optical communication demands has prompted the exploration of space-division multiplexing (SDM) using multi-core fibers (MCFs) to significantly increase transmission capacity. Among the challenges in MCF deployment, inter-core crosstalk (ICXT) remains a major limiting factor for signal integrity. This study investigates ICXT in dual-core optical fibers, analyzing its physical origin, dependence on wavelength, and sensitivity to core geometry and refractive index profiles, while also evaluating techniques for its mitigation. Using coupled mode theory (CMT) simulations, we systematically quantify crosstalk behavior over a 10 km fiber length. Our results indicate that crosstalk is strongly wavelength-dependent, with measured values of –32 dB at 1550 nm for a 50 µm core pitch and –38 dB at 1310 nm, highlighting the enhanced mode overlap at longer wavelengths. Reducing the core pitch from 50 µm to 40 µm increases the crosstalk to –28 dB, demonstrating the critical influence of core spacing on coupling strength. The introduction of trench-assisted cores, characterized by a low-index annular region surrounding each core, effectively reduces ICXT by approximately 10 dB, achieving –42 dB at 1550 nm for the same pitch, while heterogeneous core designs exploiting different propagation constants further suppress coherent crosstalk accumulation. Additionally, fiber bending is shown to slightly modify crosstalk levels, emphasizing the need for mechanical stability in practical deployments. These findings establish a clear relationship between core design parameters, wavelength, and ICXT, providing actionable guidelines for fiber engineers. The study confirms that a combination of trench-assisted structures, optimized core spacing, and refractive index tailoring can achieve low-crosstalk dual-core fibers suitable for high-capacity SDM systems. Overall, this work contributes a comprehensive understanding of inter-core interference mechanisms and highlights effective strategies for mitigating crosstalk, supporting the design of next-generation optical networks with enhanced spectral efficiency and reliability. The quantitative analysis presented herein provides a basis for further experimental validation and paves the way for the development of low-crosstalk MCFs optimized for long-haul and metropolitan optical links.