To get rid of the complex analogue control loops that are traditionally used in resonator fiber optic gyroscope (R-FOG) and to meet the requirements of high accuracy as well as small-size and light-weight in Inertial Navigation Systems (INSs), a digital controller is developed and demonstrated experimentally to control the R-FOG with the digital serrodyne modulation. The digital controller is designed to implement the function of tracking the laser diode frequency drift and to compensate for the imperfect 2π modulation voltage of the phase modulator for the serrodyne modulation. To acquire the resonant frequency, the digital serrodyne modulation with symmetric frequency shift is adopted as a counter-measure for Rayleigh backscattering noise. The optimal serrodyne modulation generated frequency shift is decided to be in the range of 100~120 kHz according to the numerical calculation. The successful demonstration of the open loop operation with the digital controller is deemed as the basis for the digitalized closed-loop experiment in future.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.