Stress distribution analysis in multi-core fibers: birefringence and polarization-mode dispersion characteristics

We explore the birefringence characteristics of multi-core fibers (MCFs) and their relationship to polarization-mode dispersion (PMD) performance, aiming to identify the factors contributing to variations in PMD across various MCF designs. The analysis centers on numerically evaluating the residual thermal stress distributions generated by the regions composed of different materials within the MCF to determine the birefringence in the cores. Three previously reported and experimentally fabricated MCF designs with varying parameters and documented PMD measurements were used as references for this study. The results reveal that factors such as core distribution, core pitch, core refractive index profile, and cladding diameter play pivotal roles in defining the birefringence and PMD characteristics of MCFs. Based on these findings, we suggest that designing MCFs with cores arranged in a square lattice and an optimized core pitch can significantly reduce birefringence compared to alternative core distributions, potentially achieving PMD performance comparable to that of conventional single-mode fibers.