Three common principles of fibre optic temperature measurement are exemplarily examined: fibre Bragg gratings, Raman scattering and interferometric point sensors. Based on the shift of the Bragg wavelength, fiber Bragg grating (FBG) sensors have been employed to measure a variety of physical parameters such as stress, strain, displacement, temperature, vibration and pressure. Most of these measurement tasks can be carried out using conventional electric temperature sensors, but with limitations. This review provides a comprehensive overview of FBG sensor technology.