Nitrogen-doped silica-core fibres for Bragg grating sensors operating at elevated temperatures

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 degrees 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.