High Sensitivity Interference Torsion Sensor Based on Dumbbell Fiber

In the field of engineering testing, fiber interferometric torsion sensor is used to measure the magnitude of torsion, and their sensitivity needs to be further improved and identify the direction of torsion. To improve the internal stress distribution when the fiber is twisted and increase the modulation of the twist on the refractive index of the fiber core, we designed and manufactured a dumbbell-shaped end structure fiber and constructed an interference torsion sensor with a structure of single-mode fiber dumbbell fiber single-mode fiber. The experimental results indicate that its torsional sensing sensitivity is 0.65 nm/(rad/m). When pretwisted to a pitch of
$450 ~\mu \text{m}$
on the dumbbell fiber, it has sensitivities of 2.13 and −1.57 nm/(rad/m) in both forward and reverse torsion directions, respectively. Meanwhile, the sensor can measure physical quantities such as refractive index, temperature, and strain, with sensitivities of 237 nm/RIU, −27 pm/°C, and −10 pm/
$\mu \varepsilon $
, and has the advantage of resisting temperature crosstalk. The interference torsion sensor based on dumbbell fiber will play an important role in engineering monitoring.