Abstract: An improved ring laser gyroscope is disclosed that uses two counterrotating beams separated in frequency by an amount that is large compared to lock-in thresholds. The two beams are heterodyned together to obtain a beat frequency whose magnitude is proportional to rotation rate. In the preferred embodiment, the gyroscope utilizes an optical fiber waveguide as the laser cavity. The two countercirculating beams are generated via the mechanism of stimulated Brillouin scattering within the cavity. The two Brillouin ring lasers are pumped by two beams derived from an external pump laser. The derived beams are shifted in frequency by acousto-optic modulators. Lock-in is eliminated at all rotation rates. Other error sources common to ring laser gyroscopes are eliminated or greatly reduced.