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A dual-wavelength erbium-doped fiber laser with bow-tie polarization maintaining regenerated fiber Bragg grating (PM-RFBG) as a sensor head is proposed. The PM-RFBG with enhanced thermal resistance is obtained through isothermal annealing treatment towards a saturated seed grating. The optical signal to noise ratio (SNR) is higher than 61 dB and the 3 dB line width is less than 18 pm at room temperature. The temperature characteristic of the laser sensor is investigated at temperatures ranging from 200 °C to 800 °C. The temperature sensitivities of the laser wavelength in fast (λf) and slow (λs) axes are 16.2 pm °C−1 and 15.1 pm °C−1, respectively. The simultaneous measurement of force and temperature could be realized at temperatures ranging from 200 °C to 400 °C, for the force sensitivities of λf and λs are 1.333 nm F−1 and 1.346 nm F−1, respectively. Due to the cross-sensitivities of temperature and force, the force sensitivity shows an approximately linear increase at temperatures between 400 °C and 600 °C. The dual-wavelength laser sensor is capable of operation at temperatures up to 800 °C due to the high optical SNR and narrow line width. [ABSTRACT FROM AUTHOR]

The characterization of a fiber Bragg grating in pure-silica-core and Ge-doped-core optical fiber is demonstrated under tensile strain at different temperatures. The peak wavelength of the fiber Bragg grating increases slowly under tensile strain of 1000 µε when the temperature exceeds a certain value. The wavelength response of the pure-silica-core fiber Bragg grating is less sensitive under the same high-temperature strain as compared with the Ge-doped-core one. The results show a little predominance for the pure-silica-core fiber Bragg grating in high-temperature strain sensing. The two kinds of fiber Bragg grating are capable of measuring temperatures of up to 800 °C, but it is recommended that strain measurements are conducted below 500 °C to ensure good stability and repeatability. [ABSTRACT FROM AUTHOR]