Fig. 1. Schematic of U-shaped optical fiber cavity filled with liquid crystal

Fig. 2. Schematic of experimental system. (a) Schematic of experimental setup; (b) photograph of liquid-crystal-filled U-shaped fiber device; (c) microscopic photograph of U-shaped fiber cavity

Fig. 3. Interference spectra corresponding to structure before filling liquid crystal, ordinary wave after filling liquid crystal, and extraordinary wave after filling liquid crystal, respectively

Fig. 4. Characteristics of interference spectra when temperatures are below clearing point of liquid crystal. (a) Transmission spectra of ordinary and extraordinary waves at different temperatures; (b) dip wavelength as functions of temperature for dip A and dip B, respectively

Fig. 5. Characteristics of interference spectra when temperatures are above clearing point of liquid crystal. (a) Transmission spectra at different temperatures; (b) dip wavelength as a function of temperature for dip C

Fig. 6. Refractive index of liquid crystal E7 versus temperature