A system includes an optical waveguide, provided as a component of a first part, and at least one sensor system, provided as a component of a second part. The second part is movable relative to the first part, and the optical waveguide radiates light laterally on the side. The sensor system detects the light intensity of the laterally emitted light emitted by the optical waveguide. A grating is provided between the sensor system and the optical waveguide.