Add to ORKGA fiber optics sensor (10) and method for attaining accurate measurement are provided. A polarization maintaining optic fiber (22) forms a linear optical path. An optical element (24) is used to convert linearly polarized light waves to circularly polarized light waves which propagate along the optical path and pass through a sensing medium (24). Because of external stresses and disturbances, the optical element (24) introduces light of the wrong state of polarization into the optical path. The result is a scale factor error in the measurement and an extra incoherent D.C. light detected at the detector (36). The presence and magnitude of the extra incoherent D.C. light is used to provide a normalizing factor to compensate for the scale fact...