Toshio Danzuka

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.

High-speed deposition of graded-index fiber by the multiflame vapor axial deposition method

The high-speed deposition of VAD porous preform has become economically possible by utilizing the multiflame VAD method.1 In high-speed VAD of graded-lndex fibers, It is important to improve on the yield percentage of raw material and the controllability of the refractive-index profile. Graded-index fibers were fabricated at a deposition rate of 3–5 g/min by utilizing the multiflame VAD method. A raw material yield of 70% and high bandwidth of more than 1 GHz · km were achieved.