Development of a health monitoring system using a thermal-resistant fiber Bragg grating for fast reactor power plants; Performance evaluation of a thermal-resistant FBG for strain measurement

Saruta, Koichi   ; Tsukimori, Kazuyuki; Shimada, Yukihiro; Nishimura, Akihiko  ; Kobayashi, Takao*

A thermal-resistant fiber Bragg grating (FBG) fabricated by femtosecond laser processing was examined to evaluate the performance as a strain sensor, compared with a conventional FBG sensor. Each FBG was affixed on a stainless-steel beam along with a strain gauge to measure the Bragg wavelength shift as a function of strain. We used the intensity of the reflection spectra from the FBGs as a weighting factor to determine the Bragg wavelengths. Although the strain sensitivity for the thermal-resistant FBG was found to be 0.34 pm/, a measurement accuracy of 3 was able to be achieved by employing the Bragg wavelength determination algorithm, which was comparable to a measurement accuracy of 2 for the conventional FBG sensor.