Disclosed is a differential fiber-optic frequency-modulated continuous-wave(FMCW) Sagnac gyroscope for measuring rotation velocity. The gyroscopecomprises a frequency-modulated laser, two fiber-optic polarizers (P1 and P2),twoY-type single-mode fiber-optic couplers (FC1 and FC3), two X-type single-modefiber-optic couplers (FC2 and FC4), a single-mode fiber coil and a photodiode.Thetwo output fibers of FC1 and FC3 are connected with the two input fibers ofFC2and FC4, the first output fibers of FC2 and FC4 are connected with the fibercoil,and the second output fibers of FC2 and FC4 are directly connected to eachother toform an optical fiber shortcut, as shown in Fig. 1. The laser is driven by agatedmodulation signal. The gyroscope uses the phase difference between the beatsignalfroin the fiber coil and the beat signal from fiber shortcut to measure therotationvelocity. The advantages of this gyroscope include high accuracy, long dynamicrange, good long-term stability, compact size and light weight.
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