Fiber optical temperature measuring apparatus

Abstract From the Canadian patent

A fiber optical measuring apparatus in accordance with the invention utilizes the thermal shift of the absorption edge in doped insulators such as colored glass filters. A radiant energy source is operable in a first, normal mode for temperature measurement and, is selectively operable in a second mode for calibration purposes. In the first mode, the source emits light at a wavelength extending into the absorption edge and, in the second mode emits light at a wavelength removed from the absorption edge and at which transmission of the light through the sensing element is not affected by temperature shift. A reference photodetector coupled to the radiant energy source to receive light …