Fig. 3.

Schematic of the LCFBG detection algorithm. The ratio γ(λ) is computed by normalizing the measured spectrum; a sample γ(λ) in non-uniform conditions is reported. The three regions R1, R2, and R3 are treated separately. A peak tracking technique simply computes the two side peaks in R1 and R2, relatively to previous calibration in uniform heating conditions, estimating the temperatures at both sides. The inner part is first filtered to smooth noise, then integrated, and normalized for a calibration function, obtaining the slope function ξ(λ), as in the bottom plot. The three thermal data are then combined returning the temperature profile on the whole distance axis.