Bragg gratings in standard nonhydrogenated fibers for high-temperature sensing

Abstract

Fiber Bragg gratings engraved in standard telecommunications-grade single-mode fibers without previous hydrogen loading show enhanced thermal stability for high-temperature measurements up to 800 °C. The reflectivity decay at that temperature is adequate for industrial applications with a weekly change of sensing heads.

Fibre Bragg Gratings, towards a Better Thermal Stability at High Temperatures

“…Speciality fibres were drawn using different dopants in the glass composition [Butkov et al (2006), Groothoff and Canning, (2004)] or other materials [Grobnic et al (2007)], quenching and annealing processes were applied either as pre-or post grating inscription [Chisholm et al (1998), Aslund and Canning (2000), Coradin et al (2013)], femtosecond laser pulses were used to write the grating by a point by point method [Martinez et al (2004)], among others. Resulting performance increased from a few hours at 800°C [Groothoff and Canning (2004)] -using a Boron co-doped fibre optic -to about 300 hours at 600°C in standard G.652 telecommunications grade fibre optic [Oliveira et al (2011)], as depicted in the graph on Fig. 1.…”

A microfiber coupler tip thermometer

“…Because of their immunity to electromagnetic interference and possibility to work in contact with explosives, the use of optical fibers for temperature monitoring has been widely investigated [1][2][3][4]. Among optical fiber devices, fiber Bragg gratings (FBGs) [1,[5][6][7][8][9][10][11][12] are possibly the most common tool used for temperature sensing. FBGs inscribed in telecom optical fibers can reach temperatures T as high as 800 o C [8].…”

“…Among optical fiber devices, fiber Bragg gratings (FBGs) [1,[5][6][7][8][9][10][11][12] are possibly the most common tool used for temperature sensing. FBGs inscribed in telecom optical fibers can reach temperatures T as high as 800 o C [8]. Silica optical fibers have been shown to be capable to measure temperatures in excess of 1000 o C [10][11][12], but they require specialty fibers and/or a long manufacturing process which includes hydrogen loading, a cumbersome grating writing equipment working with toxic gases and a relatively long post fabrication annealing.…”

Fast-Response High-Temperature Microfiber Coupler Tip Thermometer

“…Fiber Bragg gratings (FBGs) [3][4][5][6] are possibly the most commonly investigated optical fiber devices for temperature monitoring, as they can reach temperatures as high as 800 ºC [7] when inscribed in telecom optical fibers. In addition, regenerated FBGs written in silica optical fibers have been shown to be capable to reliably stand 1000 ºC [8] and reach temperatures as high as 1295 ºC [9], but they often require special fibers, hydrogen loading, a cumbersome grating writing equipment working with toxic gases and post fabrication treatments.…”