Recent research on passive and active resonator fiber optic gyros are discussed. Basic research on the noise factors and the countermeasures in the R-FOG have been accumulated. The research to reduce the size of the system has also been carried out. System configurations of the B-FOG as well as the characteristics of the fiber Brillouin ring laser have been investigated. The B-FOG has the possibility to realize wide dynamic range with a simple configuration.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.