High sensitivity fiber ring laser torsion sensor with ultra-wide linear response and ultra-high resolution

In this paper, a high sensitive fiber ring laser torsion sensor (FRLTS) with ultra-wide linear response and ultra-high resolution is designed and experimentally demonstrated. An elliptical core fiber (ECF) based Sagnac loop interferometer (SI) is utilized as a torsion sensing element as well as a filter in the FRLTS. Experimental results demonstrated that the maximum linear torsion measurement range of the torsion up to 340°, and the linear torsion sensitivities are 0.10 nm/°and −0.10 nm/° in the clockwise and counterclockwise direction, respectively. Due to the use of the fiber ring laser, the spectrum of the torsion sensor exhibits narrow linewidth and high signal-to-noise ratio, which is beneficial to enhance the resolution of the sensor. It achieves a high resolution of 0.43°, which is at least 2.3 times in comparison to that of previous reported FRLTS scheme and 47.4 times in comparison to that of interferometer-based scheme with the same type fiber. The proposed sensor possesses the advantages of wide linear response range, high resolution, high sensitivity and easy fabrication, which has great potential of applications in the field of aviation, medical, health monitoring.