Measurement of Pump-Induced Temperature Increase in Doped Fibers Using Whispering-Gallery Modes

Accurate measurement of the pump-induced temperature increase in rare earth doped optical fibers has been carried out based on the excitation of whispering-gallery modes resonances of the doped fiber itself. Variations of fiber temperature are found from the wavelength shift of the resonances. The narrow bandwidth of the resonances (few hundredths of a picometer) provides a temperature resolution better than 10^-2°C at room temperature. The technique is all-optical and it does not require processing of the doped fiber.