Bidirectional oscillations in Er-doped fiber ring cavity with polarization splitting for rotation sensing

► Bidirectional single-mode oscillations are achieved in Er-doped fiber ring. ► Introducing an unique polarization splitting method to control mode coupling. ► Two types of mode coupling along with their distinctive effects are identified. ► The phenomenon of beat frequency adjusting has never been reported. ► The rotation test result shows a good agreement with the theoretical predictions.