细芯长周期光纤光栅构成的湿度传感器

Humidity sensor composed of thin core long period fiber grating

利用高频CO2激光器分别在细芯光纤和普通单模光纤中刻写了光栅周期参数相同的长周期光纤光栅,然后采用提拉法分别在这两个长周期光纤光栅的包层表面涂覆了聚乙烯醇(PVA)薄膜,构造了两款光纤湿度传感器。对比研究了这两款光纤湿度传感器的湿度与温度传感特性。实验结果表明,两款湿度传感器通过解调透射谱的波长偏移,实现了环境相对湿度(RH)的测量。同时,在环境湿度高时具有很高的湿度灵敏度,在环境湿度低时灵敏度较低。细芯长周期光纤光栅湿度传感器对湿度变化的响应时间短响应速度更快,同时它对环境温度变化的敏感度低,环境温度变化对湿度测量交叉敏感小。设计的湿度传感器结构简单、成本低、制作方便、灵敏度高、响应快速,在分析化学、环境监测和生物传感方面有一定应用前景。

Using high frequency CO_(2) lasers,long-period fiber gratings with the same grating period parameters are engraved in thin core fiber and ordinary single mode fiber,respectively. Then two fiber humidity sensors are constructed by coating polyvinyl alcohol( PVA) film on the cladding surface of the two long-period fiber gratings by pull method.The humidity and temperature sensing characteristics of these two optical fiber humidity sensors are compared and studied. Experimental results show that the two humidity sensors can measure the relative humidity( RH) of the environment by demodulating the wavelength shift of transmission spectrum. At the same time,it has high humidity sensitivity when environmental humidity is high,and low sensitivity when environmental humidity is low. The response time of thin core long period fiber grating humidity sensor to humidity change is faster,at the same time,its sensitivity to ambient temperature change is low,and the cross sensitivity of ambient temperature change to humidity measurement is small.The designed humidity sensor has the advantages of simple structure,low cost,convenient fabrication,high sensitivity and fast response,and has a certain application prospect in analytical chemistry,environmental monitoring and biosensing.