增敏型级联双参量测量的光纤传感器

Sensitivity-enhanced cascade dual-parameter measurement optical fiber sensor

旨在有效解决液体折射率检测中温度和折射率交叉敏感的问题,研制了一种增敏型光纤光栅(FBG)级联马赫-曾德尔(M-Z)结构的温度、折射率双参量测量的光纤传感器。通过多次熔接实验,调节相应参数将单模光纤(SMF)和薄芯光纤(TCF)进行拉锥熔接;然后在TCF的另一端熔接无心光纤(NCF),制备出M-Z光纤干涉仪;再在NCF末端级联上铝制毛细管增敏封装后的光纤光栅(FBG),最终完成双参量测量的光纤传感器的制备。根据M-Z干涉原理及FBG模式理论,计算了增敏FBG理论的温度灵敏度,给出了传感器的灵敏度系数矩阵与温度、折射率与透射谱的波长漂移量的理论公式。搭建了温度、折射率传感测试系统,实验结果表明:在15~85℃温度范围内,随着温度增加,该传感器的透射谱逐渐红移,封装后的FBG和M-Z结构的温度与波长偏移量线性相关系数分别为0.96323和0.91577,温度灵敏度分别为33.71 pm/℃和11.58 pm/℃;在室温下(25℃),液体折射率在1.333RIU~1.34235RIU范围内,随着折射率增加,FBG透射谱不发生偏移,M-Z透射谱逐渐蓝移,折射率与波长偏移量线性相关系数分别为0和0.98761,折射率灵敏度分别为0 nm/RIU和-493.51322 nm/RIU。该传感器可以有效提高温度、折射率的检测精度和灵敏度,可应用于环境、生物、石油化工和食品生产等领域。

To solve the problem of cross-sensitivity between temperature and refractive index in liquid refractive index detection,an optical fiber sensor for temperature and refractive index dual parameter measurements of a sensitivity-enhancing fiber Bragg grating(FBG)cascaded Mach-Zehnder(M-Z)structure is proposed in this paper.First of all,through multiple welding experiments,the single-mode fiber(SMF)and thin-core fiber(TCF)are tapered and welded adjusting welding parameters.Then,the other end of the TCF is fused with the head of the coreless fiber(NCF)to prepare a miniature M-Z optical fiber interferometer.Finally,the fiber grating(FBG)encapsulated by aluminum capillary sensitization is cascaded at the end of the coreless fiber to complete the preparation of the optical fiber sensor for dual-parameter measurement.According to the M-Z interference principle and the FBG mode theory,the temperature sensitivity of the sensitized FBG theory is calculated,and the sensitivity coefficient matrix of the sensor and the theoretical formula of the wavelength offset of the temperature,refractive index and transmission spectrum are given.A temperature and refractive index sensing test system was built.The experimental results show that in the temperature range of 15~85℃,with the increase of temperature,the transmission spectrum of the sensor gradually shifts toward long wave.The linear correlation coefficients of the temperature and wavelength offset of the packaged FBG and M-Z structures are 0.96323 and 0.91577 respectively,and the temperature sensitivity is 33.71 pm/℃and 11.58 pm/℃respectively.At room temperature(25℃),the refractive index of liquid is in the range of 1.333 RIU to 1.34235 RIU,as the refractive index increases,the FBG transmission spectrum doesn′t shift,but the M-Z transmission spectrum gradually shifts toward shot wave.The linear correlation coefficients of refractive index and wavelength offset are 0 and 0.98761 respectively,and the refractive index sensitivity is 0 nm/RIU and-493.51322 nm/RIU respectively.The proposed sensor can effectively improve the detection accuracy and sensitivity of temperature and refractive index,and can be applied in the fields of environment,biology,petrochemical industry and food production.