A fiber optic sensor is developed in order to measure film thickness along a curved surface. The technique is non-invasive, which has large bandwidth and good spatial resolution (150 μm and 300 μm). A “finger” type surface is used on top of which liquid is poured down in a continuing manner. Film thickness is measured with the fiber optic probe on 2 different locations along the “finger” surface. Film thickness of 163 and 79 μm was measured near the top and in the middle of the fin surface.