Fig. 1. Relationship between effective refractive index of micro-nano fibers and external refractive index with different diameters

Fig. 2. Brillouin frequency shift of 2 μm micro-nano fiber versus external refractive index

Fig. 3. Experimental system diagram

Fig. 4. Brillouin scattering peaks in single mode fiber and micro-nano fiber

Fig. 5. Frequency shifts of Brillouin peaks at different refractive indexes. (a) Brillouin frequency shift of peak a; (b) Brillouin frequency shift of peak b

Fig. 6. Linear fitting of Brillouin frequency shift related to refractive index