A fiber-optic temperature sensor based on spectrum detection

A fiber-optic temperature probe based upon spectral photo metric detection of the change in wavelength of the optical absorption edge of a semiconductor sensor has been tested. Broadband light is coupled into optical fiber by a focusing lens, transmitted through the sensor - a small prism of GaAs - attached to the end of a two-fiber probe. The return light through a collimating lens is analyzed by a fast-scanning spectrometer consisting of a diffraction grating and a silicon photodiode array. The silicon photodiode array can detect the spectral line distributed in specific angle by the diffraction grating. The analog output signal is transited to digital signal which is inputted into microprocessor. The system has been applied in the measurement of the temperature in Celsius ranging from 20 to 175.