We describe a fibre Fabry-Pérot heat-transfer sensor that is capable of performing the high-spatial-resolution measurements required in turbomachinery research. The all-fibre cavity operates as a calorimeter embedded perpendicular to the test surface. The cavity incorporates a Bragg grating as the internal reflector, producing a mechanically robust sensor suitable for aerodynamic measurements. We present experimental results from an impinging flow rig, comparing the optical sensor with a thin-film resistance gauge subjected to a step increase in heat flux of 30 kW m^-2.