Dual-wavelength erbium-doped fiber laser with polarization maintaining regenerated gratings for high temperature and force measurement.

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 (λ_f) and slow (λ_s) 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 λ_f and λ_s 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]