A differential all-birefringent-fiber frequency-modulated continuous-wave Sagnac gyroscope is described. The gyroscope employs a birefringent fiber coil to construct a double unbalanced fiber optic Sagnac interferometer and uses the phase difference between the two beat signals from the fiber coil to measure the rotation velocity. The advantages of this gyroscope include doubled rotation sensitivity and less nonreciprocal phase drift.
A practical reflectometric fiber optic displacement sensor is reported. The sensor is based on the principle of optical frequency-modulated continuous-wave (FMCW) interference and primarily consists of a single-mode laser diode, a Y-type fiber optic directional coupler, and a quarter-pitch gradient-index lens. The displacement of the target is determined by measuring the phase shift of the beat signal with a special signal-processing method. An accuracy of 0.02 µm in a measurement range of 1000 µm has been achieved.
A practical double-sensor multiplexed fiber optic displacement sensor is reported. The sensor is based on the principles of optical frequency-modulated continuous-wave (FMCW) interference and frequency-division multiplexing. The beat signals from the individual sensors are assigned in the frequency domain and separated with different electrical bandpass filters. The displacements of the targets can be determined simultaneously by detecting the phase shifts of the corresponding beat signals. The cross talks between the individual sensors are analyzed algebraically and with a phasor diagram. An accuracy of 0.05 µm in a dynamic range of 1000 µm is achieved.
An all-birefringent-fiber frequency-modulated continuous-wave (FMCW) Sagnac gyroscope is described. The rotation velocity of the gyroscope is determined by measuring the phase shift of the beat signal produced by the two counter-propagating laser beams in the birefringent fiber coil. A resolution of 0.02 deg/sec with a 100-m fiber coil has been observed.
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