Fig. 1. Schematic of interrogation system based on dual-phase-shifted fiber grating

Fig. 2. Principle of microwave photonic filter based on dual-phase-shifted fiber grating. (a) Reflection spectrum of fiber grating with two phase shifts;(b) power spectrum of microwave photonic filter based on phase-shifted fiber grating

Fig. 3. Operating principle of proposed interrogation system. (a) Original states; (b) when measurand changes are experienced by phase shift at central frequency of fp2; (c) when only ambient temperature changes; (d) when carrier frequency fluctuates

Fig. 4. Measured results. (a) Measured transmission spectrum of phase-shifted fiber grating; (b) measured frequency response of dual-passband microwave photonic filter

Fig. 5. Microwave signals produced after OEO is closed

Fig. 6. Measured output microwave frequency change of OEO when different strains are applied on one of two phase shifts in the dual-phase-shifted fiber grating

Fig. 7. Applied strain as a function of beat frequency measured in experiment (small blue squares represent experimental results and blue solid line represents linear fitting result)