Ultrahigh Resolution and Sensitivity Fiber Ring Laser-Based Vector Torsion Sensor With Wide Measurement Range

We experimentally demonstrated an ultrahigh resolution and sensitivity fiber ring laser-based torsion sensor (FRLTS) with a wide measurement range in this article. The FRLTS is constructed by a fiber ring laser (FRL) in which a single stress-applying fiber-based Sagnac interferometer (SSAF-SI) is employed as both a torsion sensing component and a filter. Due to the use of FRL, the spectrum of the torsion sensor exhibits a narrow full-width at half-maximum (FWHM) and high side-mode suppression ratio (SMSR), which significantly enhances the resolution of the sensor. The experimental results demonstrate that the ultrahigh torsion resolution of the FRLTS reaches up to 0.015 rad/m and the maximum torsion sensitivity of 1.97 nm/rad/m can be achieved. This resolution and sensitivity are eight times and 7.3 times higher than those of the currently highest records of the FRLTS, respectively. In addition, the FRLTS with SSAF-SI achieves a wide measurement range from 0° to −380° in the counterclockwise direction that is 6.9 times wider than the torsion sensor with only the SSAF-SI. Meanwhile, the torsion direction can also be recognized in the torsion angle range from −120° to 220°. The sensor has the potential for application in aerospace, road and bridge monitoring, and equipment attitude monitoring due to its significant advantages, including ultrahigh resolution, ultrahigh sensitivity, wide measurement range, and directional torsion angle recognition.