A bidirectional single-longitudinal-mode Er-doped fiber ring laser was proposed. Based on it, a fiber laser gyroscope was
demonstrated. With circularly polarized lights in the Er-doped fiber, and linearly polarized lights in the rest part of the
ring, a reciprocal structure was obtained, and the spatial hole burning effect was suppressed. In the experiments, the
lock-in threshold rotation rate was 6 o/s. When the rotation rate was beyond 6 o/s, a beat RF signal of over 30-dB noise
was observed and a good linear relation between the beat frequency shift and cavity rotation rate were obtained. Finally,
the beat frequency stability was tested for 20 o/s clockwise cavity rotation.