Abstract: An optical fiber position sensor utilizes a passive gray code encoded sensor head gray code for improved reliability. Optical energy is propagated to the sensor head over a plurality of optical fibers. At the sensor head, the optical energy is either reflected back along the same fiber or absorbed by the sensor head. The presence or absence of reflected optical energy on each fiber determine each bit state for a digital word. The sensor head is attached to a device to be monitored. Movement of the device causes translatory displacement of the sensor head relative to the fibers, thereby changing at least one bit state.