Role of air pressure inside fiber holes during fabrication of long period gratings in bandgap fibers via electrode arc discharge

It has been recently demonstrated the fabrication of Long Period Gratings (LPGs) in hollow-core air-silica photonic bandgap fibers by means of pressure assisted Electrode Arc Discharge (EAD). The EAD procedure properly combined with air pressure inside fiber holes enables the localized modification of hole size and shape in both core and cladding region avoiding holes collapsing. LPGs are fabricated with a step-by-step approach by periodically repeated EAD treatment. In this paper, the role of pressure inside the fiber holes has been experimentally investigated in order to achieve design criteria of novel hollow core devices.