【作者】 罗彬彬；

【导师】 周晓军；

【作者基本信息】 电子科技大学 ， 光学工程， 2012， 博士

【摘要】 光纤Bragg光栅（Fiber Bragg Grating，FBG）以其抗干扰能力强、波长解调、绝对测量、便于复用等优点，已广泛应用于大型建筑结构、电力系统、石油化工等领域的温度、应变、压力的监测，其应用中的多参数交叉敏感问题的研究是一个重要课题。最近十年来，随着生物化学、医学、生命科学等学科的快速发展，各类光纤光栅折射率传感器，也逐渐成为光纤传感技术与这些学科的交叉领域的研究热点之一。本文以FBG为对象，主要针对目前FBG折射率传感器研究中的一些基本问题进行更深入的研究和讨论，并研究FBG传感器的多参数交叉敏感特性，将其应用于生物膜反应器内的热物理参数的传感。论文的主要内容可概括如下：1.详细介绍和对比了近十年的各类光纤光栅折射率传感器技术，总结和分析了它们在生化传感领域的研究、应用现状及发展趋势；总结了目前FBG的交叉敏感问题的研究现状。2.在现有的单端腐蚀型FBG折射率传感器的研究基础上，提出更加完善的单端腐蚀型FBG对折射率与温度同时测量的理论模型，深入分析其主要结构参数对折射率灵敏度和线性度的影响，仿真结果表明：可通过减小FBG腐蚀区域的直径或选择光栅周期较大的FBG制作单端腐蚀型FBG来增加其折射率灵敏度，但这同时会降低传感器的线性度及增大其折射率灵敏度的理论误差。基于此理论结论，建立单端腐蚀型FBG在低折射率区(1.333~约1.360)对折射率测量的线性近似和理论误差分析方法。然后，制作单端腐蚀型FBG用于简易生物膜反应器内生物膜厚度（或膜折射率）及其温度的同时测量。实验结果表明：传感器具有较好的线性度，且折射率灵敏度为6.894nm/RIU，若采用波长分辨率为1pm的光谱分析仪，则其对生物膜厚度和温度的分辨率分别为15.36±0.85μm和0.12oC。3.研究腐蚀型FBG在折射率为线性分布的非均匀液相介质下的响应特性，仿真结果表明：腐蚀型FBG的反射谱的带宽、微谐振峰个数、非对称程度等都随折射率沿FBG轴向的分布梯度、折射率在FBG两端的差值的增大而增大；特别在低折射率区（1.330~1.360），腐蚀型FBG反射谱的最大微谐峰与最小微谐振峰之间的波长差与折射率梯度之间可近似为线性关系。基于此理论结论，建立了相应的折射率梯度传感的线性近似理论模型；同时，制作剩余直径为5.73μm的腐蚀型FBG，通过实验研究验证理论仿真和分析的合理性及基于腐蚀型FBG的折射率梯度传感器在现实应用中的潜在可行性。4.研究腐蚀型高斯切趾FBG的Bragg波长、谐振峰幅值、3dB带宽对折射率的响应特性，与腐蚀型均匀FBG折射率传感器的特性进行比较。实验结果表明：腐蚀型高斯切趾FBG的Bragg波长和谐振峰幅值随折射率的变化规律，与由均匀FBG制成的腐蚀型FBG的一致，但前者的3dB带宽随折射率的增大并逐渐接近包层折射率或纤芯折射率时而越来越小，且反射谱也逐渐趋于平滑。5.从普通FBG传感器的物理机理角度推导其在“温度－横向压力”及“温度－轴向应力－横向压力”作用下的交叉敏感的理论模型。仿真结果表明：随着外界参数、光纤材料参数及Bragg波长的变化，交叉敏感项的值也以一定规律变化。基于此理论结论，提出一些如何在实际测量中减少系统误差和提高测量精度的有效方法。此外，设计和制作三维FBG温度传感阵列用于生物膜反应器内温度场的准分布式测量，并分析了其传感单元的“温度－横向压力”交叉敏感效应对温度测量误差的影响程度，实验结果表明：三维FBG温度传感阵列应用于工业中生物膜反应器内温度场的准分布式监测是可行和有效的，而且，较传统的热电偶阵列测量的方法能够获得更多的温度数据、更高的温度灵敏度和分辨率，其中的传感单元的温度灵敏度在12.11pm/oC~13.55pm/oC之间，当使用波长分辨率为1pm的光谱分析仪时，温度灵敏度最大的FBG传感单元的温度分辨率可达0.074oC。更多还原

【Abstract】 Thanks to the advantages of immunity to strong interference, wavelengthdemodulation, absolute measurement and multiplexed sensing capability, fiber Bragggrating (FBG) sensors have been widely applied in the monitoring of temperature, strain,and pressure in the fields of large building structure, electric power system,petrochemical industry, and so on. In these fields, the study on its cross-sensing problemof multi-parameters is an important subject. In the past decade, as the rapiddevelopment of the biochemistry, medical science and life science, the refractive index(RI) sensors based on the fiber gratings have been gradually become one of theresearching focuses in the crossing fields between the fiber sensors and these subjects.In this dissertation, some basic problems of the FBG RI sensors are researched anddiscussed in detail, and the cross-sensing characteristics of multi-parameters of the FBGsensor are researched as well, and then the FBG sensors are applied in the measurementof the thermo-physical parameters in the bio-film reactor. The main contents of thedissertation are given as follows:1. Various RI sensors based on fiber gratings developed in the past decade aresummarized and compared. Their current research status, current applications status andtrend of development in the biochemical fields are summarized and analyzed in detail aswell. Then, the current research status of the cross-sensing problem of multi-parametersof the FBG sensor is summarized.2. Based on the existing researches of the single-end etched FBG RI sensor, amore completely theoretical model of its simultaneous measurement for the RI andtemperature is proposed, and the impact of its structured parameters on its RI sensitivityand linearity is analyzed in detail. The simulated results show that the RI sensitivity of asingle-end etched FBG can be enhanced by decreasing the diameter of its etching regionor by selecting a FBG with a relatively bigger grating pitch for its fabrication, but thesemethods will lower the linearity of the sensor and increase the theoretical error of thesensor in the RI measurement. Based on these theoretical results, the correspondingmethodology of linear approximation and error analysis of the sensor for RI measurement at the low RI area (1.333~about1.360) are established. In addition, asingle-end etched FBG sensor is fabricated and used in the simultaneous monitoring forthe bio-film thickness (or bio-film RI) and temperature in a simple bio-film reactor.Experimental results show that the sensor has a good linearity and RI sensitivity of6.894nm/RIU, and its resolution for the bio-film thickness and temperature is15.36±0.85μm and0.12oC, respectively, in the condition of the spectrum analyzer withwavelength resolution of1pm being used.3. The responsive characteristics of the etched FBG under uneven liquid mediumwith the RI distribution being linear are analyzed. The simulated results show that theband-width, the number of the micro-resonant peaks and the asymmetric degreed of thereflection spectrum of the etched FBG will increase as the increase of the RI gradientalong its axis and the D-value of the RI at both of its ends. In particular, the D-value ofthe wavelength between the maximum and the minimum micro-resonant peaks isapproximately linear related to the RI gradient at the low RI area (1.330~1.360). Basedon these theoretical results, the theoretical model for the linear-approximationmeasurement of the RI gradient by the etched FBG is established. And then, an etchedFBG with residual diameter of5.73μm is fabricated. Through the experimentalresearch, the rationality of the theoretical simulation and analyses and the potentialapplication of the RI gradient sensor based on the etched FBG are verified.4. The responsive characteristics of the Bragg wavelength, resonant-peakamplitude and3dB bandwidth of the etched Gaussian-apodized FBG to the RI areresearched and compared to that of the etched uniform FBG RI sensor. Experimentalresults show that the changing regulations of Bragg wavelength and resonant-peakamplitude of the etched Gaussian-apodized FBG with the RI are in accord with that ofthe etched uniform FBG. However, the3dB bandwidth of the etched Gaussian-apodizedFBG will become more and more narrow as the RI increase to the cladding or coreindex, at the same time, its reflection spectrum will become more and more smooth aswell.5. The theoretical cross-sensing model of the normal FBG affected by“temperature-pressure” and “temperature-strain-pressure” are deduced and analyzedfrom the perspective of its physical mechanism. The simulated results show that thevalues of cross-sensing term of the “temperature-pressure” and “temperature-strain- pressure” will change in a certain regulation with the changes of external parameters,fiber parameters and Bragg wavelength. Based on these theoretical results, somevaluable suggestions about how to reduce the systematic error and improve themeasurement accuracy in the practical applications are put forward as well. In addition,a three-dimensional temperature sensing array based on FBG sensors is designed andfabricated to measure the temperature distribution field in an industrial bio-film reactor,and the impact induced by the cross-sensing effect of the “temperature-pressure” of itssensing unit on the error of temperature measurement is analyzed. Experimental resultsshow that the three-dimensional temperature sensing array based on FBG sensors usedto measure the temperature distribution field in the industrial bio-film reactor is feasibleand effective. Compared to the traditional methods of thermocouple array, thethree-dimensional temperature sensing array based on FBG sensors can gain moretemperature data, higher temperature sensitivity and resolution. The temperaturesensitivities of these sensing units are from12.11pm/oC to13.55pm/oC, and thetemperature resolution of the FBG sensing unit of the maximum temperature sensitivitycan reach0.074oC, by using the spectrum analyzer with wavelength resolution of1pm.更多还原