SCL-band optimised femtosecond high-order fibre Bragg grating for simultaneous strain and temperature measurement

Design and femtosecond laser fabrication of high-order fibre Bragg gratings with precisely controlled absolute wavelengths and spectral separation between higher-order resonances are presented. The line-by-line inscription technique ensures relatively high and similar reflection coefficients for neighbouring harmonics. A high-order fibre Bragg grating was fabricated to operate within the SCL-band, matching the spectral range of commercially available fibre optic interrogators. The gratings were experimentally verified as an easy-to-use sensor for accurate simultaneous strain and temperature discrimination. The proposed approach addresses key limitations in dual-parameter sensing through a single compact structure, flexible spectral design, and straightforward application and compatibility with existing interrogation systems.