Single-crystal sapphire high temperature sensing based on broadband polarimetric interferometer

An optical high temperature sensor is presented based on a broadband polarimetric interferometer (BPI). The state of polarization of the broadband incident light is modulated by the high birefringence of one single crystal sapphire disk and becomes a wavelength-encoded signal, which is detected by an optical spectrum analyzer (OSA). An internally developed algorithm is employed to directly measure the differential optical path length between the two orthogonal linearly polarized light signals in the sapphire disk, which is a function of temperature. A wide dynamic measurement range (from room temperature up to 1600 degrees Celsius) with resolution less than 1°C and accuracy 0.26% full scale is achieved. The great advantages of this sensor are its simplicity and long-term stability in the harsh environment