Herein, two sets of interference spectra corresponding to the ordinary and extraordinary waves are obtained by combining the nematic E7 liquid crystal (LC) with a U-shaped optical fiber cavity and applying an external electric field to the LC. In particular, their differing temperature characteristics are investigated. Experimental results show that when the temperature is below the LC’s clearing point, the interference spectrum of the extraordinary wave blue-shifts, whereas the spectrum of the ordinary wave generally red-shifts with the increasing temperature. As the temperature approaches the LC’s clearing point, these shifts become increasingly faster. However, when the temperature is above the clearing point, the polarization dependence of the structure vanishes; further, the interference spectrum blue-shifts as the temperature increases. Then, the temperature coefficients of the refractive index in case of the LC are theoretically analyzed, which is consistent with the experimental results. The proposed system is compact, highly integrated, and stable, denoting its considerable potential in fields such as LC temperature characterization, polarization optics, and optical sensing.