The FU-E40 Fibre Unit (FU Series) uses an area light to detect targets passing in various positions. The amplifier makes it possible to ignore gradual changes in light intensity caused by dust or dirt, ensuring that only sudden light intensity changes caused by a passing target are. Sensors come in a wide variety, and each type has strengths and weaknesses. This section provides a detailed look at fiber optic sensors. What Is a Sensor? Learn all about the principles, structures, and features of eight sensor types according to their detection principles. Fibre optics feature two distinct components, an amplifier and sensor heads. The FU Series offers a wide variety of options including thrubeam, reflective, retro-reflective and definite reflective sensing heads.