In this work a spatially-resolved fiber optic temperature sensor has been characterized in a wide range of gradient applied on its active area (from −35 °C to +35 °C). Preliminary experiments to assess its feasibility for application in laser ablation have been performed. The sensor under test is a linearly chirped fiber Bragg grating (FBG), with 1.5 cm-length of active area. It can be considered as a chain of several FBGs, each able to sense local temperature. The sensor response to the gradient has been analyzed in terms of its spectrum width (full width at half maximum). There is a linear relationship between the full width at half maximum and the gradient, with a sensitivity of 0.0087 nm°C⁻¹. The feasibility test using the linearly chirped FBG during laser ablation showed promising results: it is able to detect both the thermal gradients along is active area and the average temperature increment during the procedure.