Long-term thermal stability tests at 1000 °C of silica fibre Bragg gratings made with ultrafast laser radiation

Abstract

Using an ultrafast Ti:sapphire 800 nm laser and a phase mask, fibre Bragg gratings (FBGs) with high thermal stability were fabricated in Ge-doped SMF-28 fibre for sensor applications and were subjected to long annealing tests at 1000 °C. FBGs that maintained more than 99.95% reflectivity after several hundred hours at this temperature are demonstrated. The gratings perform well in cycling experiments up to 1000 °C, and hysteresis in the wavelength response was not detected. At a temperature of 1050 °C, a permanent drift of the central wavelength is observed which is associated with a reduction of the grating strength. The capability of this new type of FBG to be used for high temperature sensors is discussed.

Regenerated Fibre Bragg Gratings

“…Previous studies have already established that the operable temperature of FBGs can be increased by several means, including tailoring the glass composition [Shen et al 2007;Butov et al 2006], pre-processing with seed irradiation [Åslund & Canning 2000;Canning et al 2001], the formation of type-In (or type IIA) [Xie et al 1993;Dong et al 1996;Groothoff & Canning 2004] gratings and type-II [Archambault et al 1993;Hill et al 1995] gratings, including those inscribed using femtosecond IR lasers [Grobnic et al 2006]. For a general review on photosensitivity and grating types, see [Canning 2008a].…”

Ultrafast femtosecond-laser-induced fiber Bragg gratings in air-hole microstructured fibers for high-temperature pressure sensing

“…These highly desirable advantages have resulted in significant efforts to improve the hightemperature stability of FBG sensors. In particular, the adaptation of novel fibers, such as nitrogen-doped fiber [5], or novel fabrication techniques, such as ultrafast laser writings [6], has potentially improved the operational temperature of fiber grating devices to be on par with FPI-based sensors, approaching or exceeding 800°C.In this Letter, we apply femtosecond-pulsed ultrafast laser writing to produce high-temperature stable FBG in two-hole fibers for pressure sensing. This work demonstrates a significant improvement of the operational temperature of FBG pressure sensors in air-hole microstructured fiber to over 800°C.…”

“…These highly desirable advantages have resulted in significant efforts to improve the hightemperature stability of FBG sensors. In particular, the adaptation of novel fibers, such as nitrogen-doped fiber [5], or novel fabrication techniques, such as ultrafast laser writings [6], has potentially improved the operational temperature of fiber grating devices to be on par with FPI-based sensors, approaching or exceeding 800°C.…”

Femtosecond pulse written fiber gratings: a new avenue to integrated fiber technology

“…Fertein et al wrote LPG and operated them successfully at 1000°C [60]. These findings were confirmed for FBGs by various groups, both for direct [86] and phase mask written gratings [87][88][89][90][91]. Figure 5 depicts the reflectivity of conventional and femtosecond pulse written FBG at high temperatures [86].…”