A popular fiber optic sensor, the Fotonic sensor is a displacement sensor containing two groups of fiber optics, one set connected to a light source and termed the transmitting fibers, and the other set connected to a photo detector (photodiode) and known as the receiving fibers. These two groups of fibers are bundled into a common probe.
Referring to the schematic below, the light generated from the source is channeled through the transmitting fibers to the probe tip. The light then travels to the target surface and part of it is reflected back to the probe. A portion of the reflected light is caught by the receiving fibers and transmitted to the photo detector where its intensity is measured. The intensity of the reflected light is a function of distance (gap) between the probe tip and the target surface.
Typical Fotonic Sensors