Abstract: The active ring gyrometer comprises a path closed by mirrors (11,12,13) forming a resonant cavity (10) in which is placed a cell (20) containing an optically non-linear medium which permits by a four wave mixture the coherent auto-oscillation of two conjugated counter-rotative waves. The gyrometer further includes two pumping laser beams (31, 32), an optical device (40) for irradiating the medium of the cell, an optical system (50) for causing these two waves to interfere, and a detector (60). The optically non-linear medium and the intensity modulators (70) of the pumping beams permit the production of an optical "bias" which eliminates the blind zone in which the gyrometer is unsuitable for measuring relatively low rates of rotation.