Refractive Index Profile Changes Caused by Arc Discharge in Arc-Induced Long-Period Fiber Gratings

摘要

Long-period fiber gratings were inscribed in a commercial silica fiber by a point-by-point arc discharge technique with different discharge conditions. The index profile change induced by arc discharge was measured using the quantitative phase microscopy for the first time. The causes of the transmission variations induced by different arc discharges and the mechanisms of the index profile change were investigated based on the measured index profiles. The refractive indexes in the core and the cladding were decreased and increased by arc discharge, respectively. The central dip in the core index profile almost disappeared, and the index gradient became gradual. The resonance wavelengths were fluctuated by discharge current and time owing to variations of the reduction of the core-cladding index difference and the extent of the index change region.