Strain sensor applications of fiber Bragg gratings

Abstract

Sensing properties of fiber Bragg grating (FBG) strain sensors produced in photosensitive optical fibers was the main task of the presentation. Several Bragg gratings were made by the scanning phase mask method. The standard telecom matched-clad fibers were used in the experiment but it was necessary to hydrogenate them before the UV illumination. We have hydrogenated our fibers for up to 30 days under the pressure of 130 bar. The double frequency 244 nm 100 mW Coherent argon ion laser was used. Bragg gratings spectral characteristics were measured, filter central wavelength and FWHM determined. Grating were stretched and their strain sensitivity determined. FBG was also attached to the surface of elastic bar. It was bended in the grating squeeze and stretch configurations. The linear response of the Bragg wavelength shift was observed in all experiments. Total wavelength shift of 10 nm was easily measured by our monochromator system in the range ±4355 με. The experimental results were compared to theoretical data obtained from simple model bar equations. We have found good agreement between theory and experiment. FWHM values remained nearly unchanged. We believe the model simplicity as the source of small discrepancies.