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 degrees C to 800 degrees C. The temperature sensitivities of the laser wavelength in fast (lambda f) and slow (lambda s) axes are 16.2 pm degrees C-1 and 15.1 pm degrees C-1, respectively. The simultaneous measurement of force and temperature could be realized at temperatures ranging from 200 degrees C to 400 degrees C, for the force sensitivities of lambda f and lambda 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 degrees C and 600 degrees C. The dual-wavelength laser sensor is capable of operation at temperatures up to 800 degrees C due to the high optical SNR and narrow line width.