Micronor Inc.’s Model MR330, a fiber optic absolute position sensor with an all-optical design, is immune to electromagnetic interference such as lightning, radiation or magnetic fields. The fiber optic aspect of the sensor makes it suitable for long-distance position sensing over hundreds of meters without being affected by ground loop problems. The sensor uses an optical technique embedded in a passive sensor and active controller connected by a duplex fiber optic link. The controller transmits a burst of light to the code disk in the sensor, which accurately modulates the spectral components of the light based on angular position. The position information is imprinted in the optical spectrum of the light and is guided back to the controller for precise position readout.