The measuring principle of fibre optic temperature measurement is based on the backscattering of a short laser pulse (< 10 ns) coupled into the glass fibre. A fiber optic LHD uses standard fiber optic sensor cables, typically over lengths of several kilometers, that function as linear temperature sensors. These systems are. Infrared thermography (IRT) is representative of non-contact temperature measurement technology, which can avoid direct contact between temperature measurement equipment and high-temperature areas to achieve non-destructive testing [19, 20, 21]. This is done by adding a periodic variation to the refractive index of the fiber core. ▪ One of the main advantages of this technology is its iiiiintrinsic. Lower temperature targets--say from -100°C to 400°C--can be measured by activating various sensing materials such as phosphors, semiconductors or liquid crystals with fiber optic links offering the environmental and remoteness advantages.
