An optical fiber sensor may include an optical fiber configured to receive a light having a first frequency from a light source and to transmit the light through the optical fiber, the transmitted light having the first frequency and a second frequency which is generated by stimulated Brillouin scattering (SBS), a photodetector configured to receive the transmitted light from the optical fiber and to convert the transmitted light into an electric signal and a sensing circuit configured to calculate an average squared value of the electric signal received from the photodetector, which is dependent on a frequency difference between the first frequency and the second frequency.