Optical-Fiber Pyrometer Positioning Accuracy Analysis

The influence of the distance between the fiber end and the machined surface on temperature measurements in a twocolor fiber-optic pyrometer is analyzed. The propose fiber-optic pyrometer is capable of measuring highly localized temperatures, while avoiding the use of lenses or fiber bundles, by using a standard graded index glass fiber OM1 with 62.5/125 core and cladding diameters. The fiber is placed very close to the target and below the tool insert. The output optical power at both wavelength bands is theoretically and experimentally analyzed for a temperature of 650 degrees C at different fiber positions in a range of 2mm. The results show that there is no influence of the fiber position on the measured optical power and therefore, on the measured temperature.