Fabrication and characterization of long-period-grating temperature sensors using Ge–B-co-doped photosensitive fibre and single-mode fibre

Abstract

Fabrication and temperature sensitivity were studied for long-period gratings (LPGs) in a high-Ge photosensitive fibre and the standard single-mode fibre. Using a high-Ge fibre, the irradiation time with a KrF excimer laser can be decreased to one order of magnitude less than that of the single-mode fibre. LPGs in the single-mode fibre near the dispersion turning point showed a large wavelength shift to the longer wavelength during the irradiation, and even after the irradiation the wavelength continued to shift in the same direction. Diffusion of hydrogen into the core is considered to be responsible for the latter wavelength shift. Increase in the temperature sensitivity by a grating period near the dispersion turning point was discussed. The absolute value of the temperature sensitivity of an LPG in a photosensitive high-Ge fibre was about 1/3 of that of the single-mode fibre, and the dependence on fibre materials and the fabrication conditions was discussed.