Modeling and Testing of Uniform Fiber Bragg Gratings Using 1-D Photonic Bandgap Structures in Microstrip Technology

A way to model and test fiber gratings and fiber grating-based systems in the microwave range is proposed. The method rests on the equivalence relationship found between a fiber grating and a one-dimensional microstrip photonic bandgap structure that consists of a periodic pattern of circles etched in its ground plane. The equivalence assures that the frequency-response of the fiber grating is an upshifted replica of the corresponding frequency to its equivalent microstrip device. Both apodized and nonapodized uniform fiber gratings have been considered and the feasibility of the proposed method has been shown in simulation and measurement.     

Modeling and Testing of Uniform Fiber Bragg Gratings Using 1-D Photonic Bandgap Structures in Microstrip Technology

A way to model and test fiber gratings and fiber grating-based systems in the microwave range is proposed. The method rests on the equivalence relationship found between a fiber grating and a one-dimensional microstrip photonic bandgap structure that consists of a periodic pattern of circles etched in its ground plane. The equivalence assures that the frequency-response of the fiber grating is an upshifted replica of the corresponding frequency to its equivalent microstrip device. Both apodized and nonapodized uniform fiber gratings have been considered and the feasibility of the proposed method has been shown in simulation and measurement.     

Time-resolved photoacoustic spectroscopy using fiber Bragg grating acoustic transducers

An acoustic transducer based on a fiber Bragg grating (FBG) is presented and characterized for use in time-resolved laser-induced photoacoustic spectroscopy (PAS) on solid samples. The photoacoustic wave was generated by pulsed laser excitation of immobilized carbon black or erbium oxide powder, and detected by recording either the transmission or reflection spectrum of a clamped fiber Bragg grating (FBG). The characterization of the FBGs photoacoustic response is based on the experimental comparison with a static lateral strain source and on theoretical analysis using the piecewise-uniform approach to photoelastic theory. The temporal resolution of the response is determined by the arrangement of the FBG with respect to the source of the acoustic wave and is better than 150 ns, as was verified in a deconvolution analysis.The method has not only a fast time response but also is simple, inexpensive, and accurate as indicated by the good agreement of the experimental photoacoustic spectrum with previous measurements.     

Fiber Bragg gratings for dispersion compensation in optical communication systems

This paper presents an overview of fiber Bragg gratings (FBGs) fabrication principles and applications with emphasis on the chirped FBG used for dispersion compensation in high-speed optical communication systems. We discuss the range of FBG parameters enabled by current fabrication methods, as well as the relation between the accuracy of FBG parameters and the performance of FBG-based dispersion compensators. We describe the theory of the group delay ripple (GDR) generated by apodized chirped fiber gratings using the analogy between noisy gratings and superstructure Bragg gratings. This analysis predicts the fundamental cutoff of the high frequency spatial noise of grating parameters in excellent agreement with the experimental data. We review the iterative GDR correction technique, which further improves the FBG quality and potentially enables consistent fabrication of FBG-based dispersion compensators and tunable dispersion compensators with unprecedented performance.     

一种新颖封装的耐高温光纤Bragg光栅温度传感器

分析了光纤Bragg光栅的传感原理,将光纤光栅置于细钢管通过一种耐高温胶粘结细钢管两端使光纤光栅在高温下不脱落,并通过细钢管上的中间螺纹给光纤光栅施加预应力,使光纤光栅在温度变化过程中一直保持张紧状态,保证传感器有很好的重复性和良好的线性.实验结果表明:该FBG光纤光栅温度传感器灵敏度为0.0252 nm/℃,有良好的重复性和线性,温度测量范围达200℃以上,可应用在高温环境测量温度的变化.     

相位修正的耦合模理论用于计算光纤Bragg光栅法布里-珀罗腔透射谱

基于光纤Bragg光栅(FBG)反射复振幅相移对FBG法布里-珀罗腔透射谱的影响,分析了传统耦合模理论计算均匀FBG反射复振幅相移产生误差的原因.引入折射率分布初始相位参数描述FBG折射率分布纵向的微小偏移,用真实的反透射系数代替简明形式的反透射系数,对传统耦合模理论进行了修正,增加了与折射率分布初始相位参数有关而与波长无关的相位因子.在此基础上进一步对计算非均匀FBG的传输矩阵法的相位进行了修正.修正后的快速计算结果用于FBG法布里-珀罗腔透射谱的计算,可反映折射率分布初始相位参数对透射峰波长位置的影响,与Rouard 算法及实验值均有较好的一致性. 关键词： 光纤Bragg 光栅 法布里-珀罗腔 耦合模理论     

Analytical investigation of response of birefringent fiber Bragg grating sensors in distributed monitoring system based on optical frequency domain reflectometry

When Fiber Bragg gratings (FBGs) are used as strain sensors, both longitudinal and lateral strain can be applied uniformly or non-uniformly over the length of the FBGs. In order for the demodulation of such FBG signal, this paper investigates the response of birefringent FBGs which are monitored by distributed measurement system based on optical frequency domain reflectometry. A numerical model of the distributed measurement system is built based on piece-wise uniform approach, which considers polarization states of propagating lights. The numerical model simulates analytical response of birefringent FBGs especially when birefringence induces power fluctuations in the distributed spectra, which can be noise or new opportunity for sensitive monitoring of birefringence. Simulation results show the relationships between the power fluctuations and the polarization states of the propagating lights. Consequently, appropriate methods of polarization control for sensitive distributed birefringent FBG monitoring are discussed.     

Modeling and testing of static pressure within an optical fiber cable spool using distributed fiber Bragg gratings

Based on the force analysis, we establish a theoretical model to study the static pressure distribution of the fiber cable spool for the fiber optic guided missile (FOG-M). Simulations indicate that for each fiber layer in the fiber cable spool, the applied static pressure on it asymptotically converges as the number of fiber layers increases. Using the distributed fiber Bragg grating (FBG) sensing technique, the static pressure of fiber cable layers in the spool on the cable winding device was measured. Experiments show that the Bragg wavelength of FBG in every layer varies very quickly at the beginning and then becomes gently as the subsequent fiber cable was twisted onto the spool layer by layer. Theoretical simulations agree qualitatively with experimental results. This technology provides us a real-time method to monitor the pressure within the fiber cable layer during the cable winding process.     

DBR掺镱光纤激光器激射波长的研究

对基于一少量模光纤光栅和一普通光纤光栅的分布布喇格反射掺镱光纤激光器的激射波长进行了详细研究.通过对普通布喇格光栅的中心波长进行调谐,发现激射波长始终是由两光栅卷积的最大值所确定的等效反射峰值相对光栅反射峰值的偏移以及激射波长相对等效反射峰值的偏移两种机理共同决定的,通过实验证明两种偏移量均不受限于光纤光栅的带宽.对实验结果进行了分析总结.     

基于分布式光纤Bragg光栅传感技术的光缆卷盘静态压力研究

基于对光缆卷盘缆层静态压力分布的理论分析, 建立了光缆缠绕体系中的受力理论模型. 研究表明, 随着缠绕层数的增加, 卷盘各层光缆所受压强先快速增大而后变化平缓. 采用分布式光纤Bragg光栅(FBG)对光缆绕线装置上缆层的静态压力进行了实时传感, 理论上给出了FBG的中心波长偏移量与体系压强的定量关系, 实验上发现各层FBG的中心波长随着光缆卷盘缠绕层数的增加先较快速变化而后趋于平缓, 理论模拟和实验测量结果符合得很好. 该技术解决了光缆绕线过程中无法对缆层所受压力进行实时监测的难题.     

光纤布喇格光栅作为增益均衡器的掺铒光纤EDFA放大器

采用平均反转率模型分析了带光纤布喇格光栅的增益平坦掺铒光纤放大器,其输出增益可由一组耦合超越方程描述,而非耦合微分方程,同时讨论了用于增益平坦的布喇格光栅的最佳位置设计作为增益建模和最佳设计实例,对于输入功率0.5mW位于1545～1552nm的8个波长信道,得到的输出增益不平坦度小于0.05dB.最后还证实了布喇格光栅作为增益均衡器具有高输出功率和功率转换效率的优越性.     

D形光纤Bragg光栅弯曲灵敏度的理论和实验研究

用材料力学理论分析了D形光纤Bragg光栅（D-shaped fiber Bragg grating,D-FBG）以及常规光纤Bragg光栅由弯曲引起的轴向应变,得到了光栅Bragg波长漂移的弯曲敏感特性.实验结果和理论计算结果基本相符.与常规FBG相比,该D-FBG的弯曲灵敏度要高近80倍.因此D-FBG可以直接应用于弯曲形变的测量,以及间接应用于压力、加速度等物理量的测量.理论分析和实验结果对采用该类型光纤光栅的器件和传感系统的设计具有参考意义.     

Diametric load sensor using a fiber Bragg grating and its differential group delay analysis

Different from the basic sensing theory of the fiber Bragg grating (FBG) sensors based on spectral analysis, a new method exploiting the polarization properties of FBG for diametric load sensing is proposed. In this paper, the evolution of the differential group delay (DGD) response of FBG with respect to the diametric load is completely studied. The centroid information of the DGD evolution of FBG is subsequently proposed for diametric load sensing. Experiments were carried out to verify the reasonability and feasibility of the sensing method. Good agreements between experimental results and numerical simulations had been obtained.     

基于神经网络的光纤光栅应变传感器重构

提出一种基于径向基函数神经网络模型来重构蜕化的光纤光栅应变传感器的方法.以结构健康监测系统中应变测量系统的光纤光栅应变传感器之间关联分析为基础,依据径向基函数神经网络强大的函数逼近能力,利用关联度高、运行良好的应变传感器去重构蜕化的应变传感器,保证重构的应变传感器与蜕化传感器有较高的数据准确度.实验结果证实了该方法在理论和实践上的精确性和可行性.     

对光纤布拉格光栅法布里-珀罗腔纵模间隔问题的研究

对光纤布拉格光栅(FBG)法布里-珀罗(F-P)腔的透射特性进行了深入分析,指出了FBG F-P腔透射谱中纵模位置的影响因素,讨论了与普通F-P腔的联系和区别.应用光栅的有效镜面模型对FBG反射主瓣内反射系数的相位因子进行线性模拟,定义了FBG有效长度的概念并得出其表达式.提出将FBG的有效长度纳入到FBG F-P腔的等效腔长中,用等效腔长来计算FBG F-P腔中的纵模间隔.数值仿真和实验结果都表明,用等效腔长计算所得的纵模间隔与实际的FBG F-P腔中的纵模间隔符合很好,误差极小. 关键词： 光纤布拉格光栅 法布里-珀罗腔 纵模间隔 有效镜面模型     

有限包层半径光纤Bragg光栅的理论研究

采用光纤波导三层模型,对有限包层半径光纤Bragg光栅导模有效折射率的改变进行了理论分析,结果表明:当包层直径小于16μm时,单模光纤Bragg光栅(纤芯直径为8.3μm)的导模有效折射率才开始发生明显变化.在包层外添加外包层,通过改变外包层的折射率可以实现对光栅Bragg反射波长的调谐,同时对不同芯子直径的光栅Bragg波长移动进行了数值计算.在保证光纤归一化频率不变的前提下,芯径越小Bragg波长调谐范围越大,当包层厚度为1μm时,芯径为a＝2.2μm的光栅Bragg波长调谐范围约为3.9μm.     

光纤Bragg光栅水听器特性及实验研究

论述了光纤Bragg光栅（FBG）水听器探头基元 （FBG）的传感特性,分析了FBG的耦合系数、反射率、反射带宽和栅长对光纤Bragg光栅水听器传感特性的影响.通过改进光纤Bragg光栅水听器探头封装结构,增加了其压力敏感系数.并将实验结果与标准水听器（压电型）比较,标定出光纤Bragg光栅水听器的声压灵敏度;对传感信号进行电路解调,得出了解调结果,结果显示与原始声波信号基本一致.试验表明,在1 kHz~25 kHz的声波检测范围,光纤Bragg光栅水听器响应平坦度好,信号输出稳定,证明文中采取的改进措施是有效的.     

侧边抛磨区材料折射率对光纤光栅波长的影响

针对轮式光纤侧边抛磨法,研究了在侧边抛磨光纤光栅抛磨区覆盖不同折射率的材料时,侧边抛磨光纤光栅Bragg波长随外界折射率的改变而变化的特性.理论计算与实验结果都表明,侧边抛磨光纤光栅Bragg波长会随抛磨区覆盖材料折射率的增大向长波长方向偏移；侧边抛磨面离光栅区纤芯表面越近,覆盖材料折射率对波长偏移的影响越大.实验指出,当侧边抛磨区覆盖材料的折射率从1.389 7变到1.447 9时,Bragg波长将会发生1.402 nm的偏移.用轮式光纤侧边抛磨法制备的侧边抛磨光纤光栅可应用于光纤光栅的波长调谐或传感器.     

基于匹配光纤光栅法布里-珀罗干涉仪的应变解调方法

提出并实验验证了一种基于匹配光纤光栅法布里-珀罗干涉仪的应变传感器解调方法,该方法综合了光纤法布里-珀罗干涉技术和匹配光纤光栅滤波法的优点.通过半导体制冷片和压电陶瓷组成的闭环负反馈控制系统,精确调节匹配光栅法布里-珀罗干涉仪的温度和应变,有效解决了光栅法布里-珀罗干涉仪的失配问题,从而保证系统静态工作点处于最佳匹配位置,同时能够避免探头因环境温度波动导致的测量误差.实验结果表明,该系统能够响应50～800Hz的输入信号,应变最小分辨力至少为0.4nε/Hz1/2,解调灵敏度高,且不受环境温度波动的影响,因而在动态应变或振动测量中具有较高的实用性.     

新型光纤光栅温度自补偿方法理论分析

为了解决光纤光栅作为应变传感器使用时的温度应变交叉敏感问题,提出了一种全新的光纤光栅温度补偿方法,该方法最大特点是利用一个光纤光栅同时实现了温度自动补偿与应变测量。该方法基于材料的热应力原理,简称为基于材料热应力的光纤光栅温度补偿方法。通过理论分析表明:温度灵敏度系数与应变灵敏度必须精确测定,否则会影响结构设计;应变元件与温度补偿元件的面积之比对温度补偿效果很大,原则上应小于0.5,因此结构半径的加工误差对温度补偿影响很大。应变元件与温度补偿元件的长度比对温度补偿效果基本可忽略,因此,原则上在不影响温度补偿效果的前提下,尽量提高温度补偿元件与应变元件的长度比。