Fig. 1. SEM image of the cross section of PM-MOF

Fig. 2. Mode fielddistribution and effective refractive of fundamental modes before and after liquid filling in MOF air-hole. (a) Before liquid filling; (b) after liquid filling

Fig. 3. Schematic of all-fiber optofluidic sensing system and the PRF structure

Fig. 4. Curves of phase modal birefringence with wavelength of MOF before and after liquid filling and PRF twist period as a function of the resonant wavelength. (a) Phase modal birefringence of the MOF as a function of wavelength; (b) twist period of the PRF as a function of the resonant wavelength

Fig. 5. Transmission spectra of the PRF with Λ=17.8 mm, N=12, θeff=3.75° before and after liquid filling

Fig. 6. Output spectrum characteristics of PRF at different twist period lengths when N=12, θeff=3.75°. (a) Output spectra; (b) resonant wavelength of PRF as a function of the twist period lengths

Fig. 7. Output spectral characteristics of PRF at different numbers of twist period when θeff=3.75° and Λ=17.8 mm. (a) Output spectra; (b) coupling efficiency

Fig. 8. Output spectral characteristics of PRF at different numbers of twist period and twist angle when Λ=17.8 mm, 4Nθeff=π. (a) Output spectra; (b) coupling efficiency

Fig. 9. Transmission spectra characteristics of PRF for different microfluidic refractive index values. (a) (b) Modal birefringence dispersion of the MOF as a function of wavelength; (c) transmission spectra of PRF; (d) resonant wavelength of the PRF as a function of the microfluidic refractive index value

Fig. 10. Resizing of the cross section of PM-MOF

Fig. 11. Characteristics of microfluidic refractive index sensitivity as a function of MOF core size. (a) Phase modal birefringence of PM-MOF when liquid refractive index is 1.333 as a function of resizing coefficient α; (b) variation of phase modal birefringence of MOF with respect to microfluidic refractive index at the wavelength of 1550 nm as a function of α; (c) optofluidic refractive index sensitivity of the PRF as a function of α