In order for the resonator fiber optic gyroscope to achieve navigation grade performance, it must employ an optical frequency shifting technique for high scale factor accuracy. Serrodyne phase modulation commonly used in interferometric fiber optic gyros, has been considered a leading choice of modulation techniques. Here we present theoretical analysis on the effects of imperfect serrodyne phase modulation along with experimental results. A solution for substantially reducing the rotation sensing errors associated with imperfect serrodyne is also presented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.