Figure 8. Fluorescent fiber optic sensor probe.
One of the simplest wavelength based sensor is the
blackbody sensor as shown in Figure 9. A blackbody cavity
is placed at the end of an optical fiber. When the cavity
rises in temperature it starts to glow and act as a light
source. Detectors in combination with narrow band filters
are then used to determine the profile of the blackbody
curve. This type of sensor has been successfully
commercialized and has been used to measure
temperature to within a few degrees centigrade under
intense RF fields.