A complete sensor consists of a base unit and a plastic or fiber tube to guide the light, depending on what the application requires. Balluff's fiber optic sensors are used when a conventional optical sensor is too large or too inflexible for the application: For example, for small part detection, checking part features, part positioning, counting tasks and in robotics. These devices are most commonly used in factory automation environments. The light beam travels through the core by. A fiber optic sensor and two fiber optics made of plastic or glass fibers make up a fiber optic system.