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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-0.704nm/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。
In order to improve the detection sensitivity and detection range of the existing optical fiber pH sensor and reduce the influence of bending and temperature cross sensitivity, a thin Excessively Tilted Fiber Bragg Grating (FBGG) with pH-sensitive intelligent hydrogel as sensitive film was proposed. Grating, Thin-Ex-TFG) pH sensor. In theory, the factors that affect the sensitivity of the sensor are analyzed and the solutions to improve the sensitivity of the sensor are studied. Then, Thin-Ex-TFG pH sensors with different package thicknesses were fabricated and tested. The experimental results show that the detection sensitivity (up to -0.704nm / pH) and the response range (pH value from 2 to 7) of the Thin-Ex-TFG pH sensor are better than those of the pH sensor based on the fiber Bragg grating and long- All have improved; Compared with the standard diameter of very large dip angle fiber grating, its detection sensitivity has also been improved. In addition, increasing the thickness of the hydrogel coating or reducing the diameter of the fiber grating cladding can effectively improve the sensitivity of pH detection. The experimental results are in good agreement with the theoretical analysis.