Fusion Splicing Performance Evaluation of Hollow-Core Fiber to Hollow-Core Fiber With Different Structural Parameters

Nested anti-resonant nodeless fiber (NANF) fusion splicing with variable structural parameters is essential yet challenging for both hollow-core fiber (HCF) research and field deployment. Here, we comprehensively investigate the impact of structural parameter variations on the mode field diameter (MFD) and corresponding NANF splicing performance. Numerical simulation results indicate that the air core diameter is the dominant factor in determining the MFD of NANF, and the MFD is approximately 70% of the air core diameter. Variations of the other structure parameters hold a negligible impact on the MFD. Numerical evaluation of splicing performance reveals that, under the condition of a fixed air core diameter, splicing between NANFs with different numbers of nested tube units (e.g., 5-tube and 6-tube NANF), introduces an intrinsic coupling loss (ICL) of ∼0.045 dB, attributed to the mode field shape mismatch rather than the angular alignment, as the ICL does not vary periodically with the rotational angle. Meanwhile, variations of the other parameters contribute less than 0.01 dB ICL. Finally, we conduct an experimental evaluation of fusion splicing performance by fabricating four types of NANFs with varying nested tube units, inner tube diameters, and nested tube layers. We characterize the angle alignment sensitivity, high-order mode excitation, and back-reflection performance when various combinations of four types of NANFs are fusion-spliced. Those results of NANF fusion splicing provide valuable insights for the standardization and flexible field deployment.