细直径极大倾角光纤光栅pH值传感器

为提高现有光纤pH值传感器的检测灵敏度和检测范围,降低弯曲以及温度交叉敏感的影响,提出以pH值敏感型智能水凝胶为敏感膜的细直径极大倾角光纤光栅(Thin Excessively Tilted Fiber Grating,Thin-Ex-TFG) pH值传感器.理论上分析了影响传感器灵敏度的因素,研究了提高传感器灵敏度的方案.然后,制作出不同封装厚度的Thin-Ex-TFG pH值传感器,进行实验研究.实验结果表明:Thin-Ex-TFG pH值传感器相比基于光纤Bragg光栅和长周期光纤光栅的pH值传感器,检测灵敏度(最大可达-0.704 nm/pH)和响应范围(pH值2～7)均有提高;与标准直径极大倾角光纤光栅相比,其检测灵敏度也有所提升.此外,增加水凝胶涂覆厚度或减少光纤光栅包层直径均能有效地提高pH值检测的灵敏度,实验结果与理论分析吻合.

Study on pH Sensor Based on Thin Excessively Tilted Fiber Grating

To improve the sensitivity and detection range of the current fiber optic pH sensors and reduce the effects of the cross-interaction of bending and temperature,the thin excessively tilted fiber grating (Thin-Ex-TFG) pH sensor coated with pH sensitive smart hydrogels for the sensitive membrane was put forward in this paper.We analyzed the factors that influenced the sensitivity in theory,and the scheme of improving the sensor's sensitivity was investigated.Finally,the Thin-Ex-TFG pH sensors coated with different thickness of hydrogels were fabricated and the corresponding experiments were carried out.The results showed that both of the sensitivity (up to-0.704 nm/pH) and response range (pH 2～7) of Thin-Ex-TFG pH sensor were increased,as compared with optical fiber Bragg grating pH sensor and long period fiber grating pH sensor;while compared with the standard diameter excessively tilted fiber grating with standard diameter,the sensitivity was also improved.The study revealed that appropriately increasing the coating thickness of smart hydrogels or reducing fiber grating cladding diameter can effectively increase the pH detection sensitivity,the experiment results agreed well with the theoretical analysis.