Temperature measurement of rare-earth-doped optical fibers using a variant of the differential luminescence thermometry (Conference Presentation)

Abstract

Measurement of cooling efficiency and temperature of the doped optical fiber is critical for the development of optical refrigerators and radiation balanced lasers. Measuring the optical fiber temperature, especially for single mode fibers, is challenging. Non-contact thermometry is required because a temperature sensor which is in thermal contact with the fiber can potentially be a heat load when exposed to the scattered pump power and fiber luminescence and can lead to inaccuracies in thermometry. One of the best non-contact methods is using differential luminescence thermometry (DLT). DLT works based on the fact that the 4f electrons in rare-earths are shielded from the surroundings and host field transitions; therefore, the temperature-induced intensity changes in rare-earth material luminescence are mainly caused by changes in Boltzmann population of emitting states. We propose a variant of DLT for finding a relation between the spontaneous emission of the fiber and the temperature. Our method is based on the normalized correlation between the spontaneous emission spectrum at each temperature and the reference spontaneous emission. In this method, we chose a section of the spontaneous emission spectrum as the reference and calculate the normalized correlation factor of the spontaneous spectrum at each temperature with the reference spontaneous spectrum. We make a calibration curve, and based on the calibration curve we estimate the temperature difference from the reference. Comparisons with the conventional DLT will be presented.