Fabrication and Characterization of Long-Period Gratings in Hollow Core Fibers by Electric Arc Discharge

Recently, the fabrication of long-period gratings (LPGs) in hollow-core air-silica photonic bandgap fibers by means of pressure assisted electrode arc discharge (EAD) technique have been presented. 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 as well as the effect of the grating pitch on the transmitted spectra have been experimentally investigated to achieve the design criteria of novel hollow core devices. An appropriate perturbation of fiber structure (core and/or cladding) may change the field profile of the fiber modes and cause light coupling from the fundamental mode to higher order modes. Here, the experimental demonstration of LPG prototypes with different features exhibiting attenuation bands with depth up to 12 dB are reported. Finally, the resonant wavelength dependence on local temperature and strain changes are experimentally investigated. We believe that the fabrication of LPGs-based devices in hollow core optical fibers enable new functionalities hitherto not possible.