Minimising interconnection losses in hollow-core fibres using femtosecond laser-modified single-mode fibres

Recent advancements in anti-resonant hollow-core fibres (HCFs) have achieved attenuation as low as 0.11 dB/km, comparable to standard single-mode fibres (SMFs). HCFs confine light via anti-resonant elements functioning as Fabry-Perot resonators, typically requiring large core diameters to operate efficiently. This size difference results in significant mode-field diameter mismatches when connecting to conventional SMFs, causing high interconnection losses. We demonstrate a femtosecond laser technique to expand the SMF core diameter, effectively reducing these losses. This approach enables efficient integration of HCFs into existing optical networks.