Fig. 1. Sagnac ring sensor based on the FMF-PMF. (a) Schematic diagram of the structure; (b) A physical image of the sensor

Fig. 2. When PMF length is 20 cm, the output spectra for different lengths of FMF. (a) 0 cm; (b) 5 cm; (c) 10 cm; (d) 15 cm

Fig. 3. Schematic diagram of the FMF-PMF based on Sagnac ring fiber laser temperature sensor device

Fig. 4. The relationship curve between laser output power and pump power

Fig. 5. Output spectrum of Sagnac fiber optic laser temperature sensor based on the FMF-PMF

Fig. 6. Laser output spectra intensities recorded at 2 min intervals under 175 mW pump power

Fig. 7. Center wavelengths and peak intensity of output peaks at different times

Fig. 8. Output spectra of FMF-PMF based Sagnac ring fiber laser temperature sensors at different temperatures. (a) Heat up; (b) Cool down

Fig. 9. Relationship curve between temperature and wavelength of FMF-PMF based Sagnac rings

Fig. 10. Output spectra of PMF-based Sagnac ring fiber laser temperature sensors at different temperatures. (a) Heat up; (b) Cool down

Fig. 11. Relationship curve between temperatures and wavelengths of PMF based Sagnac rings