We are investigating a new approach to inertial rotation sensing which we refer to as an active re-entrant Sagnac system (ARS). It is aimed at rotation rates extending to very low values, as required in such amplications as navigation, guidance and geophysical measurements. It employs a multiturn fiber optic loop containing an internal optical amplifier, and uses pulsed optical signals introduced by an external laser oscillator which make multiple recirculations around the loop. Its output signal is a time-sampled sinusoidal waveform having the same frequency as the beat frequency in a standard oscillating ring laser gyro (RLG) having the same loop diameter. Like the RLG, it is basically an integrating rate gyro, in which digital cycle counting is used to determine the angle turned through. It is basically free of the mode locking effect encountered with RLG's, and has prospect for higher sensitivity to rotation. Experiments using cw light are described, which include new re-sults on removing instabilities and environmental sensitivities from fiber gyros. Initial experiments on pulsed recirculation without an amplifier are described, which affirm the basic recirculation principle. Work is beginning on development of a fiber amplifier for use in a full ARS experiment.