光纤布拉格光栅的热致衰减研究

光纤布拉格光栅的工作寿命是影响光纤光栅传感器性能的关键因素.从光纤布拉格光栅的热致衰减特性出发,以界面阻隔能模型为理论基础,以光纤光栅的反射峰值为研究对象,探讨了光纤布拉格光栅的热致衰减行为.并通过对比试验对3支不同的光纤布拉格光栅进行了600℃热加速衰减实验,初步证明即使进行了退火处理,光纤布拉格光栅的性能仍然存在热致衰减蜕化.从实验数据中得到了光纤布拉格光栅的热振动频率,建立了热致衰减曲线.预测了30℃、50℃、100℃条件下光纤布拉格光栅的反射率衰减到90％的时间分别为23年、11年和3年.     

光纤Bragg光栅的特性及应用研究

介绍了光纤光栅研制及其应用研究的情况。研究包括：光纤光栅的基本特性,光纤光栅外腔半导体单频和锁模激光器、光纤光栅稳频光纤环形激光器和主动锁模光纤激光器、基于光纤光栅的波长转换器和基于啾啁光纤光栅的可调谐激光器等。     

双光纤光栅高频加速度传感器的研究

研制了一种新型双光纤光栅加速度传感器,并对该传感器的工作原理和基本特性进行了理论分析,实测表明,这种新型双光纤光栅加速度传感器可在5～2000 Hz频率范围内获得稳定的振动信号.这不仅解决了传统悬臂梁FBG加速度传感器难以实现高频振动测量的问题,而且具有温度自补偿、谐振频率高、使用方便等优点,在高频测量中具有广阔的应用前景.     

光纤Bragg光栅应变传感中的温度补偿技术

本文对光纤光栅传感中的应变和温度交叉敏感问题进行了讨论,在此基础上提出了采用参考光栅实现光纤光栅应变传感时的温度补偿的基本原理和方法,并通过实验进行了验证.理论和实验均证明,本文提出的参考光栅温度补偿法原理简单,而且补偿效果好.     

Measurement of Material Deformation with Fiber Bragg Gratings (Summarization)

Fiber sensing elements based on Bragg gratings (FBG) are a prospective basis of sensors for detecting deformations in measuring systems, in particular, for integrated control of various structures. The possibility of their application in the structure of polymer composite material for aerospace construction elements is examined. The FBG operating principle is based on change in the period of the grating—the periodic structure of the refractive index of an optical fiber core. Change in the period can cause either thermal expansion or compression of an optical fiber. Therefore, to solve integrated control problems, one has to understand the cause of optical fiber deformation in the area of location of FBG—with change in mechanical loading applied to it or thermal operating conditions. Proposed approaches to the allowance for temperature change when measuring deformation with FBG are systemized and the results of works in this field are presented. Possible implementations of each approach are described. Measurement accuracy of deformation and temperature is determined. The structural scheme of sensing elements is described.     

树脂传递模塑成型的光纤光栅监测

复合材料固化过程对于生产高质量复合材料部件十分必要。文中利用光栅传感器监测树脂传递模塑(RTM)复合材料层板制造过程中内应变及温度,根据复合材料内应变/温度关系曲线的突变点,获得复合材料的材料转变点(凝胶点、玻璃化转变温度)信息。在复合材料降温阶段,利用光栅监测的应变/温度值计算RTM成型复合材料的内层和外层热膨胀系数。监测结果与传统检测方法相比十分一致。     

树脂传递模塑成型注模过程的光纤光栅监测

有效监测树脂传递模塑成型(RTM)的树脂注模过程对于生产大型共固化复合材料结构十分必要.本文重点讨论利用光栅传感器监测注模过程的树脂流动问题.本文在复合材料层的不同位置布置了1个温度传感器用来监测温度,2个应变传感器用来监测树脂流动前沿到达时间,试验结果表明50 min和115 min时树脂流动前沿分别到达No.1和No.2应变传感器,166 min时完成注模,此时监测温度为最低的24.59℃.光栅传感器完全可实现树脂传递模塑注模过程的监测.     

交错型采样光纤Bragg光栅的折射率调制法设计

通过改变种子光栅中相邻子光栅的折射率调制量,提出一种新型交错型采样光纤Bragg光栅(ISFBG)设计,并利用传输矩阵法分析ISFBG的反射谱特性.结果表明:对种子光栅中相邻子光栅的折射率设计不同的调制量,ISFBG的反射谱信道教增加,主反射峰的反射率主要由折射率调制量大的子光栅决定,并且其反射率的大小随着折射率调制量...     

用于实现空间滤波的体布拉格光栅的制备

探讨实现空间滤波的新方法,分析体布拉格光栅作为空间滤波器的可行性,基于Kogelnik一维耦合波理论,讨论影响体布拉格光栅衍射效率和角度选择性的主要因素.用全息法在光致聚合物中记录了体布拉格光栅,完成了激光光束二维空间低通滤波的实验.实验结果表明:在记录材料达到饱和状态之前延长曝光时间能提高衍射效率:增大入射角度能使角度选择性提高,但由于吸收加大,衍射效率反而会有所下降.因此,体布拉格光栅用作空间滤波器时要对衍射效率和角度选择性作综合考虑.     

用相位模板法制备紫外光写入光纤布拉格光栅的研究

利用相位模板，在２４８ｎｍ ＫｒＦ准分子激光器光束的照射下，在国产高掺锗单模光纤中制作出了中波长为１５４７ｎｍ，峰值反射率约为１０％，带宽为０．６４ｎｍ的调制光纤由拉格光栅。     

基于倾斜光纤光栅的传感解调技术

该文设计了一种基于倾斜光纤光栅（tilted fiber Bragg grating,TFBG）的不受温度影响的光纤布拉格光栅（fiber Brag ggrating,FBG）应变解调系统．将倾斜光纤光栅用作边沿痣波器,当周围环境温度变化时,利用倾斜光纤光栅纤芯模与包层模的温度特性与普通光纤布拉格光栅相同这一特点,无需另加温度补偿,就可以实现FBG应变传感的动态解调,消除温度噪声对应变信号的影响．由实验可知,当温度在25℃到39℃范围变化时,解调系统的性能基本不发生改变,解调范围达到6nm．     

Pressure Vessel Wall Thinning Detection Using Multiple Pairs of Fiber Bragg Gratings For Unbalanced Strain Measurements

This paper proposes a method for using a pair of identical fiber Bragg gratings to measure the unbalanced strain factor in an isothermal-mechanical system. Cascading two identical fiber Bragg gratings, the unbalanced strain factor caused by the disturbance can be interrogated from the peak difference of the two reflecting Bragg wavelengths. If the mechanical system is in an isothermal environment, the thermal variations in the Bragg grating detection system can be automatically compensated. To verify the feasibility of the unbalanced strain detection using a pair of fiber Bragg gratings, the wall-thinning monitor in a pressure vessel system was investigated. The proposed technique is easy to install, immune to electro-magnetic and thermal interference, and highly sensitive in-time to remote monitoring for fiber optic smart structures.A finite element model (FEM) is used to simulate the wall thinning in a pressure vessel system. The minimum detectable unbalanced strain and cross-talk between two reflecting Bragg wavelengths were investigated.ROC Revised for Journal of Nondestructive Evaluation, 2000     

高效率微结构光纤光栅写入技术研究

针对传统周期性气孔结构的微结构光纤光栅(MOFG)写入过程中的高写入散射问题,本文提出一种新型的大圆孔式微结构光纤光栅。其特点是用一填充适当折射率流体的大圆孔结构来代替部分周期性小气孔。当光束从外侧写入光栅时,一方面会避免传统周期性气孔结构带来的高写入散射问题;另一方面大圆孔也将起到一微透镜作用,有助于进一步提高光束写入纤芯区域的能量比例。仿真分析结果表明：新型大圆孔式微结构光纤光栅的写入效率可达到传统周期性光子晶体光纤光栅、单模光纤光栅写入效率的288%和206%左右。同时本文也提出利用对称角度写入方法来保证光栅写入场的对称性,从而改善单侧写入造成的写入场分布不均匀问题和写入致双折射问题。     

Round Robin for Optical Fiber Bragg Grating Metrology

NIST has administered the first round robin of measurements for optical fiber Bragg gratings. We compared the measurement of center wavelength, bandwidth, isolation, minimum relative transmittance, and relative group delay among several grating types in two industry groups, telecommunications and sensors. We found that the state of fiber Bragg grating metrology needs improvement in most areas. Specifically, when tunable lasers are used a filter is needed to remove broadband emissions from the laser. The linear slope of relative group delay measurements is sensitive to drift and systematic bias in the rf-modulation technique. The center wavelength measurement had a range of about 27 pm in the sensors group and is not adequate to support long-term structural monitoring applications.     

Multiplexing Scheme for Self-Interfering Long-Period Fiber Gratings Using a Low-Coherence Reflectometry

A novel multiplexing scheme based on a low-coherence reflectometry (LCR) is proposed for a sensing array (in parallel) of self-interfering long-period fiber gratings (SI-LPGs). Each SI-LPG sensor consists of an LPG and a section of fiber with a highly reflective end (mirror). The spectral information of each LPG is sensitive to some parameters of the surrounding measurand and can be reconstructed from the corresponding subreflectograms (obtained by the LCR) through a fast Fourier transformation. The sensing signals of multiple SI-LPG sensors can be multiplexed if the length of the fiber section in each sensor is set to a different value. Experiments of measuring the surrounding temperature at different sensors are demonstrated to show the good performance of our multiplexing system.     

Embossed Bragg Gratings Based on Organically Modified Silane Waveguides in InP

Considering the large variety of applications for optical glass waveguide gratings, the effective production method of embossing for micropatterning, and the unique advantages of InP-based materials, we expect that hybridization of embossed optical glass waveguide gratings and InP substrates will inevitably lead to new applications in integrated optics. We present our preliminary results of research toward the development of solgel-derived glass waveguide gratings made by embossing on InP. Theoretically, the dependence of the stop-band FWHM and transmission contrast of the grating filter on the grating length, and the relationship between the Bragg grating's reflective wavelength and the dopant concentration in the solgel waveguide, are obtained. Experimentally, using organically modified silane, we solve the problem of mismatching of SiO(2) and InP, and successfully fabricate an embossed glass grating with a second-order Bragg reflection wavelength of 1580 nm and a FWHM of 0.7 nm fabricated upon a solgel waveguide on an InP substrate.     

非相干组束中反射体布拉格光栅的衍射潜力(英文)

基于耦合波理论,提出了一种推导反射体布拉格光栅衍射效率方程的新方法.在被推导的衍射效率方程基础上,获得了平面单色和高斯光束反射体布拉格光栅衍射的详细理论模型,分析了平面单色、发散单色和多色光束的衍射效率.结果表明:平面单色波的角和谱选择性随光栅厚度和空间频率而变化,角选择性的范围从低于0.01mrad到超过100mrad,谱选择性的范围从低于0.1nm到超过100nm;当光束的角发散或谱宽等于光栅的角选择或谱选择性时,光栅能提供超过88%的衍射效率;当光束的角发散或谱宽远小于光栅的角选择或谱选择性时,光栅衍射效率下降不明显,不到平面单色波的1%.     

用于钢筋混凝土梁的光纤光栅应变传感器

在变形测定器中,光纤Bragg光栅被粘贴于内管的两端,这两端的距离确定了传感器的量规长度。为了测量拉应变和压应变,该光纤光栅必须保持处于与可能的最大压应变相等的永久性拉应变。将光纤Bragg光栅贴于H154梁的混凝土表面和H158梁的钢筋表面,以分别检测拉应变和压应变。当钢筋混凝土梁受到千斤顶的加载时,它的应变可由光纤Bragg光栅的反射Bragg波长的偏移量获得。实验表明,作为一种绝对检测器件,光纤Bragg光栅为钢筋混凝土梁提供了有效监测,其中,拉应变~1000me,而压应变~1500me。