高频CO_2激光脉冲写入PCF-LPFG传感特性研究

Sensing characteristics of high-frequency CO_2 laser pulse induced long-period fiber grating in a photonic crystal fiber

采用高频CO2激光技术在柚子型光子晶体光纤(PCF)上写入长周期光纤光栅(LPFG),并对其温度、应变和弯曲特性进行了实验研究。实验测得,PCF-LPFG谐振波长的温度和应变灵敏度分别为0.002nm/℃和0.001 8nm/με,谐振峰损耗值对温度和应变不敏感。由于高频CO2激光写入为单侧写入,导致PCF-LPFG透射谱的弯曲特性与方向和曲率直接相关。选择弯曲灵敏度较大的方向进行了弯曲测试,测得在一定的曲率范围内,PCF-LPFG的谐振波长及谐振峰损耗值的灵敏度分别为-5.45nm/m-1和3.32dB/m-1。基于PCF-LPFG的透射谱温度不敏感特性,本文为制作不受温度影响的应变和弯曲传感器提供了新的方法。

Temperature,strain and bending characteristics of a long period fiber grating（LPFG） written in a grapefruit-type photonic crystal fiber（PCF） are investigated experimentally.By using high-frequency CO2 laser,the LPFG written on PCF（PCF-LPFG） is achieved.The temperature sensitivity and strain sensitivity of PCF-LPFG resonant wavelength are 0.002 nm/℃ and 0.0018 nm/με,respectively.The PCF-LPFG resonant peak is insensitive to temperature or strain.The bending characteristics are directly related to curvature and bending direction.A direction with high sensitivity is chosen for further study.In a certain range of curvature,the bending sensitivity at PCF-LPFG resonant wavelength is-5.45 nm/m-1 and that at the resonant peak is 3.32 dB/m-1.Based on the special characteristics of PCF-LPFG,the paper provides new methods for fabricating temperature-insensitive strain and bending sensors.