Thermal Stability of Bragg Gratings Written in N-Doped- Silica-Core Fibers (original) (raw)
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Nitrogen-doped silica-core fibres for Bragg grating sensors operating at elevated temperatures
Measurement Science and Technology, 2006
Nitrogen-doped silica-core fibre is discussed in the context of a technological basis for the fabrication of Bragg gratings for sensors with enhanced temperature resistance up to 900 • C. To estimate the applicability of this fibre type for the manufacture of high-temperature Bragg grating sensors, the following features are analysed: technology for fabricating fibre preforms, fibre characteristics and particularities of Bragg gratings written therein. Experimental data on the degradation of the gratings' characteristics resulting from a long-term (up to 4 months) annealing at elevated temperatures are presented and discussed. The practical application of this type of sensor in thermometry is given as an example.
Nitrogen-doped silica-core fibres for Bragg gratings sensing at elevated temperatures
17th International Conference on Optical Fibre Sensors, 2005
Nitrogen-doped silica-core fibre is discussed in the context of a technological basis for the fabrication of Bragg gratings for sensors with enhanced temperature resistance. To estimate applicability of this fibre type for high-temperature Bragg grating sensors manufacturing, the following features are analyzed: fibre preforms fabrication technology, fibre characteristics, and particularities of Bragg gratings writing in it. Practical application of this sensor type in thermometry is given as an example.
Journal of the Optical Society of America A, 2004
Bragg gratings were fabricated in an Sn-Er-Ge-codoped silica fiber with a phase mask and ultraviolet radiation from a 248-nm KrF excimer laser. The photosensitivity of the fiber was examined by studying the initial growth rate of the gratings written into it. The thermal stability of the gratings was investigated and modeled in terms of both the refractive-index modulation and the effective refractive index of the fiber core. It was shown that the temperature-induced irreversible shift in the Bragg wavelength could not be predicted by the isothermal decay of the refractive-index modulation. Finally, the potential of the gratings written into the fiber is discussed in terms of their use in high-temperature-sensing applications.
Thermal behavior of Bragg gratings formed in germanosilicate fiber
2003
In this contribution we compare the thermal stability of type I and type IIa gratings written in germanosilicate fibers. We study and compare their central wavelengths drifts and variations of the maximum reflectivity with temperature. Also, two other important factors, the bandwidth and group delay characteristics are characterized, compared, and the differences justified, based on the gratings physical structure.
Journal of Physics: Photonics
In this paper, various types of high temperature fibre Bragg gratings (FBGs) are reviewed, including recent results and advancements in the field. The main motivation of this review is to highlight the potential of fabricating thermally stable refractive index contrasts using femtosecond (fs) near-infrared radiation in fibres fabricated with non-conventional techniques, such as the molten core method. As a demonstration of this, an yttrium aluminosilicate (YAS) core and pure silica cladding glass optical fibre is fabricated and investigated after being irradiated by an fs laser within the Type II regime. The familiar formation of nanogratings inside both core and cladding regions are identified and studied using birefringence measurements and scanning electron microscopy. The thermal stability of the Type II modifications is then investigated through isochronal annealing experiments (up to T = 1100 °C; time steps, Δt = 30 min). For the YAS core composition, the measured birefringenc...
Optical fibre Bragg gratings for high temperature sensing
20th International Conference on Optical Fibre Sensors, 2009
The development of new techniques for writing and tailoring the properties of Bragg gratings has generated a suite of distinct grating types that are optimised for performance within different temperature windows. These cover gratings produced by recipes such as hypersensitisation, thermal processing and single and multiphoton writing. In this paper, we review four types of high temperature gratings that offer comprehensive coverage of temperature space for most applications of interest. Up to 1200°C novel processing methods allow standard silica-based optical fibres to be used. However, beyond these temperatures, optical fibres made from other materials, such as sapphire, need consideration.
Bragg gratings writing dynamics and thermal annealing behavior in germanium-doped and novel nitrogen-doped silica core fibers are examined experimentally. The gratings are inscribed by a 193 nm wavelength ArF excimer laser and a phase mask. The so-called 'type IIa' Bragg gratings appear under the writing conditions used. Gratings in the fibers with different core dopants are shown to behave differently. A core corrugation occurred in optical fibers as a result of Bragg grating inscription is considered as a possible reason for the effective refractive index modulation. No changes in glass density and/or stress are required to explain 'type IIa'. The origin of core corrugation is associated with UV-induced inelastic deformation of glass and photostimulated diffusion of dopants from the core to the cladding. It is shown that the core corrugation explains features of a complicated behavior of Bragg gratings decay at elevated temperatures. The nature of a high-temperatur...
Characteristics of potential fibre Bragg grating sensor-based devices at elevated temperatures
Measurement Science and Technology, 2003
Fibre Bragg gratings (FBGs) of type I and IIA were fabricated in Ge-doped and B-Ge co-doped fibres using a 248 nm excimer laser and their performance characteristics were tested and compared with those of a chemical composition grating (CCG), written in a fluorine-germanium doped fibre, over a wide range of temperatures. Long-term testing (more than 600 h) involving a series of step-wise incremental temperature changes shows for the first time the potential of FBGs for high temperature measurement applications (up to and beyond 1100 • C), this depending on the type of FBG involved and the material and composition of the substrate fibre (the CCG was observed to be the most durable at very high temperatures). These gratings are likely to be useful for the simultaneous measurement of strain and temperature over these higher temperature ranges.
Fiber Bragg gratings for low-temperature measurement
Optics Express, 2014
We demonstrate the use of fiber Bragg gratings (FBGs) as a monolithic temperature sensor from ambient to liquid nitrogen temperatures, without the use of any auxiliary embedding structure. The Bragg gratings, fabricated in three different types of fibers and characterized with a high density of points, confirm a nonlinear thermal sensitivity of the fibers. With a conventional interrogation scheme it is possible to have a resolution of 0.5 K for weak pure-silica-core FBGs and 0.25 K using both boron-doped and germanium-doped standard fibers at 77 K. We quantitatively show for the first time that the nonlinear thermal sensitivity of the FBG arises from the nonlinearity of both thermo-optic and thermal expansion coefficients, allowing consistent modeling of FBGs at low temperatures.