Birefringent fibre frequency-modulated continuous-wave Sagnac gyroscope

A birefringent fibre Sagnac gyroscope is described, which is based on the principle of optical frequency-modulated continuous-wave interference and primarily consists of a single-longitudinal-mode frequency-modulated laser diode and a birefringent fibre coil. The rotation velocity of the fibre coil can be determined simultaneously by detecting the phase shift of the beat signal produced by two counter propagating laser beams in the birefringent fibre coil. A resolution of 0.02(degree)/s with a 100 m fibre coil has been observed. The advantages and limitation of the gyroscope are discussed.