Mode Field Diameter with Petermann II Far-Field Definition Matching for Minimized Coupling Loss between AR-HCF and SMF

In this paper, the mode field diameters (MFDs) of the fabricated AR-HCFs were experimentally investigated using near-field MFD with Gaussian approximation and far-field MFD with Petermann II definition. Our simulated and experimental results demonstrate that the coupling loss was minimized when the far-field MFD with Petermann II definition of AR-HCF matched that of reverse-tapered SMF, which was measured by a commercial fiber analysis system.