Fig. 1. Schematic diagram of Vernier effect filter

Fig. 2. Simulation results. (a) Transmission spectra of two MZIs; (b) transmission spectrum of Vernier effect filter; (c) drift of transmission spectrum of filter; (d) linear fitting

Fig. 3. Spectra of fabricated filter. (a) Transmission spectra of two MZIs; (b) transmission spectrum of Vernier effect filter

Fig. 4. Schematic diagram of fiber laser sensor

Fig. 5. Effect of pump power. (a) Influence of pump power on SMSR; (b) corresponding relationship between peak wavelength of filter and operating wavelength of laser

Fig. 6. Strain sensing results and repeatability experiment results. (a) Peak wavelength drift results; (b) SMSR of laser; (c) linear fitting; (d) repeatability experiment results

Fig. 7. Experimental results on stability of laser sensor

Fig. 8. Strain experiments with conventional sensors. (a) Envelope drift; (b) linear fitting; (c) stability test

Fig. 9. Temperature response. (a) Peak wavelength versus temperature; (b) linear fitting; (c) peak wavelength versus temperature after compensation; (d) linear fitting after compensation

Fig. 10. Fluctuation of peak wavelength of laser sensor at 0 με, 0.08 με and 0.16 με

Fig. 11. Strain sensing results after increasing magnification. (a) Transmission spectra of two MZIs; (b) transmission spectrum of Vernier effect filter; (c) drift result of peak wavelength of laser with stress; (d) multi-wavelength result

Fig. 12. Simulation results of cascading three MZIs. (a1)‒(a5) Superimposed spectra when different MZIs are cascaded; (b1)‒(b5) linear fitting