【摘要】 利用高频CO2激光脉冲写入的周期达数毫米的超长周期光纤光栅(ULPFG),实验研究了这种新型ULPFG的扭曲特性,发现它的某些高阶谐振波长漂移与扭曲率之间具有良好的线性关系和方向相关性,其灵敏度可达0·2244nm/(rad/m),是高频CO2激光脉冲写入法写入的普通LPFG扭曲灵敏度的4倍.初步的理论分析表明,新型ULPFG横截面折变的非对称性以及导模与高阶包层模之间发生的耦合使得扭曲具有方向相关性和很高的灵敏度.基于这种ULPFG独特的扭曲特性,设计了一种可判别方向的强度型高灵敏度扭曲传感器,测量灵敏度达0·4394dB/(rad/m),可满足实际应用中对扭曲低成本实时测量的要求.更多还原

【Abstract】 A high sensitivity fiber-optic torsion sensor is described,which measures twist rate and determines twist direction simultaneously by using a novel ultra long-period fiber grating (ULPFG) with periods of up to several millimeters fabricated by high frequency CO-2 laser pulses. The torsion characteristics of a ULPFG are analyzed based on the coupling theory and birefringence phenomena. The experimental results show that a higher torsion sensitivity of 0.2244nm/(rad/m) for high order resonant modes was obtained, which is four times higher than that of the long-period fiber grating written by high frequency CO-2 laser pulses. Finally, an intensity-type demodulation approach for the realization of real-time torsion measurement is proposed and demonstrated based on the edge filtering effect of the ULPFG.更多还原