Effective mode-field diameter for few-mode fibers for considering splice loss characteristics

We experimentally and numerically investigate the applicability of the conventional near-field pattern, far-field pattern (FFP), and variable aperture (VA) methods for measuring the effective mode-field diameter (MFD) of the higher-order modes, which can be used for accurately evaluating splice loss. We confirmed that the variation in the MFD values obtained with the FFP and VA methods can be converged by considering the minimum scanning angle and the minimum aperture angle, respectively, for both fundamental and higher-order modes. We reveal that the FFP and VA methods provide adequate effective MFD values for few-mode fiber (FMF), which can be used for evaluating the splice loss based on the conventional Gaussian fitting model. We also show the applicability of the effective MFD to four linearly polarized mode FMFs for considering the splice loss characteristics of each mode.