高频CO₂ 激光在扭曲的单模光纤上制作的长周期光纤光栅 (LPFG) 还原后会产生谐振峰分裂现象。基于这种光栅结构, 用拍频理论对谐振峰分裂现象和扭曲特性做了解释和分析, 实验结果与理论分析相吻合。由于这种光栅的两分裂峰具有几乎一样的温度灵敏度, 因此提出可通过测量这种光栅两分裂峰之间的距离来实现扭曲量的测量, 并且当扭曲方向不一样时, 两分裂峰的距离会变大或变小, 因此该扭曲传感器在实现高灵敏度扭曲传感时还可辨别扭曲的方向。这种传感器在工业领域将具有良好的潜在应用价值。

The resonance peak of long period fiber grating fabricated in twisted optical fiber by using high-frequency CO₂ laser pulses could split into two peaks, after the twist applied to the fiber is removed. The splitting and the torsion characteristic of the special gratings are analyzed and explained by beat-frequency theory. As the temperature sensitivity of the two splitting peaks of the grating is almost the same, it is proposed that torsion can be measured by detecting the interval change between the two splitting peaks when torsion is applied. Besides, the torsion sensor can distinguish torsion direction as the distance of the two splitting peaks increases or decreases when different torsion is applied, therefore, this kind of torsion sensors has a great potential application in high sensibility torsion sensing.