Long-period fiber grating in a pure-silica-core fiber written by residual stress relaxation

Summary form only given. Long-period fiber gratings (LPFGs) have recently been attracting much attention for their possible applications such as gain-flattening filters for erbium-doped fiber amplifiers. Most LPFGs have been written in germanosilicate optical fibers because periodic structures can be easily obtained using UV-induced refractive-index changes due to the photosensitivity of Ge-related glass defects. This technique requires that fibers for LPFGs should contain photosensitive sites, and thus it cannot be applied to those which have no photoreaction centers inside such as pure-silica core optical fibers. Here we report the efficient fabrication of LPFGs in pure-silica-core optical fibers by residual stress relaxation. We also present the thermal dependence of the loss peak of the LPFG.