SIGNAL DISTORTION INDUCED BY FRESNEL REFLECTION IN OPEN-LOOP FIBEROPTIC GYROSCOPES

The signal distortion that is due to Fresnel reflection in open-loop f iber-optic gyroscopes was theoretically analyzed to determine the rela tionship between the reflection ratio and the scale factor error of th e gyroscopes. The analysis showed that the in-phase component of each Fourier harmonic of the gyroscope signal deviates from the true sinuso idal function, a quadrature-phase component appears, and the pi/2 rota tion rates of harmonic components disagree. We evaluated the degree of scale factor degradation by defining the harmonic distortion ratio, w hich can be used as a measure for the reflectional quality of the gyro scopic optical system. The theory was verified by the response of an e xperimental gyroscope. The Fresnel reflection was eliminated by optica l and electrical means, and the signal distortion of the experimental gyroscope was suppressed. (C) 1997 Optical Society of America.