利用高频二氧化碳(CO2)激光脉冲写入法制备了一种基于少模长周期光纤光栅(LPG)的高灵敏度扭矩传感器。两个纤芯线偏振(LP01和LP11)模式耦合形成谐振峰。扭转灵敏度可达0.528 nm·rad-1·m-1, 所提扭矩传感器的扭转灵敏度比普通单模LPG提高一个数量级。引入扭转的LPG可以看作是对原光栅进行周期性螺旋调制, 其有效光栅周期与扭转率成比例, 从而使谐振峰波长发生漂移, 这是形成高扭转灵敏度的主要原因。这种新型LPG对环境折射率和温度的交叉敏感性较弱, 可以用作高精度的接触性扭矩传感器, 在涉及扭转测量的很多领域有广阔的应用前景。

A torsion sensor based on few-mode long-period fiber grating (LPG) with high sensitivity is proposed. The LPG is written by CO2-laser pulse with high frequency. Harmonic peaks are generated by the coupling between linear polarization (LP01 and LP11) modes of two cores. Torsion sensitivity can reach up to 0.528 nm·rad-1·m-1, and the torsion sensitivity of the torsion sensor is one order higher than that of the common single-mode LPG. The torsion-induced LPG can be treated as a periodic helical modulation superimposed on the original grating. As a result, the effective grating period changes in proportion to the torsion rate to make the wavelength of resonant peak drift, which is the main reason for the generation of high torsion sensitivity. Due to the weak cross sensitivity of the new LPG to ambient refractive index and temperature, the new LPG can be used as a contact torsion sensor with high accuracy and has a wide range of application prospects in the fields relation to torsional measurement.