高灵敏度长周期光纤光栅温度传感器的设计

为提高光纤光栅温度传感器的灵敏度,文中采取纤芯弹光系数大于包层弹光系数的长周期光纤光栅且在其包层外面涂覆一层随温度的升高折射率减小的薄膜材料,同时采用热膨胀系数大的金属封装光栅三种增敏措施。计算表明,增敏后的温度传感器其灵敏度系数为0.2375nm/℃,温度测量分辨力小于0.1℃。     

光纤传感技术测量气液两相流持气率研究

文中提出了一种新型气液两相流体参数测试方法。传感机理为弯曲光纤的传输光功率随外界介质折射率而变化。在分析光纤弯曲波导传输光能损耗与弯曲半径、外界折射率等因素关系的基础上,提出一种 Ｕ 型结构的光纤传感器系统,并将其应用于气液两相流体持气率测试中,进行了初步研究和探讨。     

光纤传感技术测量气液两流持气率研究

文中提出了一种新气液两相流体参数测试方法。传感机理为弯典光纤的传输光功率随外界介质折射率而变化,在分析光纤弯曲波导传光能损耗与弯曲半径,等因素关系的基础上,提出了一种 光纤传感器系统,并将其应用于气液两相流体持气率测试中,进行了初步研究和探讨。     

阶跃折射率多模光纤包层等离子体共振传感器

光纤表面等离子体共振(SPR)传感器通常以纤芯为共振基底,需要采用腐蚀、侧抛、研磨等复杂的加工工艺将光纤包层去除,存在倏逝波不易泄露,传感探针制作困难的问题。本文提出一种以光纤包层为SPR共振基底的阶跃折射率多模光纤包层SPR传感器。采用单模光纤与阶跃折射率多模光纤偏芯熔接结构,将单模光纤纤芯中的光直接注入多模光纤包层,并在阶跃折射率多模光纤包层外镀50nm金膜。在探针传感段,光场能量全部分布在阶跃折射率多模光纤包层中,发生SPR效应充分。与传统光纤包层SPR传感结构相比,该传感器能够获得更深的共振谷,折射率测量范围为1.333～1.385RIU时,传感器的平均灵敏度可达2 307nm/RIU,本文亦对传感段多模光纤纤芯直径与长度不同参数的影响进行了探究。本文提出的阶跃折射率多模光纤包层SPR传感器制作简单,有效解决了光纤包层与空气界面不易获得倏逝波的问题。     

激光束照射下大芯径SI-PDF光纤传输特性研究

应用于短距离传输的大芯径SI-PDF光纤,必须考虑漏泄光线对光纤传输功率的贡献。本文应用射线光学分析方法,推导了不同入射角的激光束与大芯径SI-PDF光纤的功率耦合传输公式,对不同入射角激光束照射下不同长度SI-PDF光纤的输出功率特性进行了实验研究。给出了在激光束照射下SI-PDF光纤光耦合功率随入射角度的变化关系曲线,并给出不同入射角度激光束在光纤中的损耗系数。结果表明：对大于12°入射的激光束,输出功率随入射角增加成指数衰减规律;不同角度入射激光束在光纤的单位长度内损耗值随角度增大而增大,在12°时损耗值为26 dB/km,在24°时达到了82 dB/km。     

流动腐蚀方式对石英光纤湿腐蚀特性的影响

为了获得光滑的腐蚀光纤表面,本文从光纤腐蚀的传质及动力学特性出发,设计了一种流动腐蚀光纤装置.采用质量百分比浓度为12.5％的氢氟酸(HF)溶液,研究了石英光纤的组成成分、腐蚀剂温度和流速对腐蚀速率以及腐蚀后光纤表面形貌的影响.实验结果及理论分析表明:光纤腐蚀速率和表面粗糙度受化学反应速率和传质速率控制;由于光纤纤芯与包层成分不同,导致纤芯腐蚀速率高于包层腐蚀速率;在静态腐蚀条件下,腐蚀速率随温度呈非线性增长,且腐蚀后光纤表面粗糙;在流动腐蚀条件下,光纤腐蚀速率提高,并与温度呈线性关系,腐蚀后光纤表面粗糙度随流速的增加呈现出先减小后增大的趋势;在流速为0.75 L/min时,获得了光滑的腐蚀光纤表面.     

光纤宏弯损耗与温度传感的理论分析

为了从理论上分析和推导光纤宏弯曲损耗与温度的关系,采用了一个平板波导近似的弯曲损耗模型,对单模光纤的宏弯曲损耗和弯曲半径、波长以及温度的关系进行了分析和仿真,得到了弯曲损耗随弯曲半径的减小而增大,波长的增大而增大,温度的升高而减小的结论。该结论对光纤弯曲损耗在温度传感器方面的应用研究起着重要的参考作用。     

多模光纤弯曲损耗特性的测量与分析

分析了多模光纤强度型微弯传感器中多模光纤的弯曲损耗。提供了弯曲半径为1mm~8mm和10mm~26mm,光源波长为0.633μm、0.780μm、0.830μm G raded Index多模光纤的弯曲损耗特性的测试结果。首次观察到了多模光纤弯曲损耗随着弯曲半径的减小而增大的趋势,以及在弯曲半径为10mm~26mm范围内损耗特性的不平滑性,并利用传播常数和W G模理论对此现象进行了解释。     

英开发出新型光纤可用于监测石油管道的泄露

英国曼彻斯特大学科学与技术研究院的费兰克·克瓦斯尼科开发出一种新型光纤 ,可用来监测石油或化学品输送管道的泄露 ,只要将这些光纤沿管道安置好 ,一旦发生泄露 ,马上可以定位并发出警报。一般通讯用光纤的内部 ,是由一个玻璃芯和覆在上面的一层透明化合物包层构成的。玻璃芯与包层的折射率不同 ,匹配适当时 ,光纤即可在其中传输而不会外泄。克瓦斯尼科研制的这种光纤 ,使用了一种含有特定化学成分的可渗透硅质包层 ,当泄露出来的被监测物质与包层中化学成分相遇时 ,即可发生化学反应 ,使包层的折射率改变 ,这样 ,光线就会从中逸出。此时…     

纤芯失配的光纤Mach-Zehnder折射率传感器

基于Mach-Zehnder干涉仪原理,利用光纤错位熔接技术设计并制作了一种单模光纤-多模光纤-单模光纤-错位熔接点-单模光纤结构的液体折射率传感器。传感器中的多模光纤和错位连接部分充当光耦合器;多模光纤在后面的单模光纤的纤芯和包层中激发出纤芯模和包层模,不同的模式有不同的模式折射率,经中间单模光纤传输到错位熔接点处时,不同模式光之间将产生光程差,经错位熔接点耦合成为导出光纤的纤芯模从而产生干涉。对该传感器输出的干涉光谱中干涉谷功率随外界溶液折射率变化的规律进行了理论分析和实验研究。结果表明：溶液折射率变化为1.358 9~1.392 2时,干涉谱中1 530 nm附近的干涉谷光功率与溶液折射率呈单调递增关系,可用于折射率的测量;折射率变化为1.372 0~1.392 2时,传感器响应曲线具有很好的线性度,线性拟合系数为0.998,对应的灵敏度为252.06 dB/RIU。该传感器制作简单、结构紧凑、成本低、灵敏度高,可用于生物医学领域液体折射率的实时测量。     

Characterization of displacement sensing based on fiber optic microbend losses

This article theoretically and experimentally characterizes single-mode fiber bending losses and associated sensing. As the bending radius decreased, the losses increased significantly, and shock phenomena were observed in the loss curve. Theoretical analysis shows that these processes were caused by coupling between fundamental models spreading in the optical fiber and whispering gallery mode spreading in the cladding and coating layers. Based on the principles of single-mode fiber bending losses, a loss modulator was designed to bend the single-mode fiber and produce losses due to external displacement. A displacement-loss model was constructed and the results were consistent with the theoretical analysis. The displacement resolving power of the loss modulator was 1 µm. The displacement measurement was from 0–350 µm, resulting in losses from 0–25 dB.     

光纤表面等离子体共振传感器理论仿真研究

为了考查光纤表面等离子体共振传感器的传感特性,基于单层膜表面Snell反射公式,利用MatLab软件仿真研究光纤表面等离子体共振(SPR)传感器的反射光谱特性,系统考查金膜厚度、待测介质介电常数以及入射到纤芯—金膜界面的入射角对反射光谱特性的影响.仿真结果表明:光纤SPR的共振波长随金膜厚度的增大而增大,随外界介质介电...     

光电互联电路中激光器与光纤间接耦合仿真分析

随着大数据、云计算、5G 通信等新兴产业的蓬勃发展,数据中心的信息量成指数增长。光电互联电路可实现数据中心服务器内部板间、组件之间、芯片之间的高速、高带宽、高密度、低功耗、低损耗的信息传输,可有效解决高速电互联技术的传输瓶颈。采用光纤作为传输介质可有效降低光电互联电路的制作成本,激光器与光纤的耦合对准技术则是实现光电互联电路的关键技术之一。文中利用ZEMAX光学软件建立了激光器与光纤间接耦合模型,仿真分析了激光器纵向偏移误差、横向偏移误差、角度偏移误差和45°耦合机构倾斜角角度加工误差对耦合效率的影响。仿真结果可为光电互联电路的设计与制造提供指导。     

基于光纤弯曲损耗的矿用乳化液浓度检测方法研究

乳化液浓度对液压支架工作性能和使用寿命有重大影响。分析了现有的乳化液浓度检测方法,根据裸光纤弯曲损耗与折射率关系的理论分析,进行了裸光纤弯曲损耗和乳化液浓度关系的实验研究,提出了通过检测裸光纤的弯曲损耗来确定乳化液浓度的方法。设计了检测裸光纤在乳化液中弯曲损耗的检测装置,并对不同浓度乳化液与裸光纤弯曲损耗关系进行了实验研究。实验结果表明,采用裸光纤弯曲损耗法可以测出乳化液的折射率,再根据乳化液折射率与其浓度的对应关系,可以间接推算出被测乳化液浓度。最后,对基于光纤弯曲损耗折射原理的乳化液浓度在线检测方法进行了研究。     

柔性硫系玻璃红外光纤传像束的制备与性能测试

讨论了红外光纤传像束的学术意义和制备工艺,制备了一种硫系玻璃红外光纤传像束并进行了专门的性能测试。选用As40S58Se2、As40S60作为芯棒和皮管玻璃组分,采用管棒法拉制成纤,利用人机结合的排丝工艺制备出了单丝直径为50μm,纤芯直径为40μm,576元正方形排列的红外光纤传像束。搭建了相应的实验测试平台,对光纤束排列规则度、断丝率、光学效率及传像束引起系统调制传递函数(MTF)下降量等指标进行了测试。测试表明,传像束断丝率为2.7%,衰减损耗低于0.5dB/m,光学效率约为31%,在红外光纤传像系统中光纤传像束引起的MTF下降量小于10%。最后,利用研制的红外传像束完成了红外成像实验,结果表明,红外光纤传像束能够实现良好的红外成像。     

长周期光纤光栅及其在通信传感领域的新应用

长周期光纤光栅是一种新型光纤器件。介绍了长周期光纤光栅的耦合机理、制备方法以及应用。其耦合机理是前向传输的纤芯基模与前向传输的各阶包层模式之间的耦合。制备原理是对光纤横向曝光,使光纤的折射率指数在轴向发生周期性变化。阐明了长周期光纤光栅用于带通滤波、光上下路复用、光纤光源、光纤耦合、偏振器件、新型传感等新技术领域的思路,给出了具体实现方法。并通过与其他方案对比,说明了基于长周期光纤光栅器件的优点,肯定了长周期光纤光栅在通信传感领域的价值。     

High-flexibility piezoelectric ribbon fiber fabrication through multi-material thermal drawing

In this study, an amorphous poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) copolymer with a high yield strain (approximately 18 %) is proposed as a cladding material for highly flexible and reliable piezoelectric ribbon fibers. Macro preforms are fabricated for thermal drawing (TD) processes, in which a poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) film is sandwiched between two electrically conductive composite sheets (carbon black (CB)/polypropylene (PP)). The piezoelectric device is cladded with the P(VDF-HFP) copolymer. The preform geometries and TD parameters are optimized to overcome the incompatibility of flow characteristics among P(VDF-HFP), P(VDF-TrFE), and CB/PP composite at the drawing temperature, yielding fibers of length more than 80 m through TD. After annealing and poling, the fiber produces approximately 5 V (peak-to-peak) under 2.5 % tensile strain and 0.5 V (peak-to-peak) under bending deformation, with a 5-mm radius of curvature. Furthermore, the piezoelectric fiber shows no severe degradation in the output voltage after 10000 cycles of bending deformation with 1-mm radius of curvature. The piezoelectric ribbon fiber developed herein has potential as a flexible tensile, pressure, or bending sensor fiber for wearable applications.

     

Optical Fiber Catheter with Distal End Bending Mechanism Control for Raman Biospectroscopy

Abstract

This work proposes the development of an optical catheter with bending control of the distal end. The probe consists of seven optical fibers wrapped in a resin and a biocompatible flexible teflon tube with a novel mechanical device that allows bending of the distal extremity to access a desired location of a human organ. A central fiber is used for tissue Raman excitation, five fibers are used for Raman signal collection, and the seventh for “optoclinical” treatment applications. Infrared, dispersive Raman spectra at 785 nm excitation were employed to optically characterize the proposed catheter. An excitation transmission loss of 16% was found compared to the traditional six collecting fibers catheter, both with their distal tip straight. By bending of the distal tip at different angles, with turning the intermediated section of the catheter around cylinders of different diameters (one finds a correlation between curvature angle of the tip and cylinder diameter), the transmission loss coefficient and transmission were determined for each distal tip angle. A transmission reduction of 5% was found for a 180° curvature. This optical catheter could be very useful in clinics, providing a way to control the fiber tip position and angle onto the tissue or organ.     

Optical fiber index profiling by video analysis of interference fringes

An electronic technique to make fringe displacement measurements on the output field of an interference microscope to 1/1000 of a fringe, not including systematic errors, is described. The method, based upon line-selected video signal analysis, is applied to the evaluation of the refractive index profile of a graded index optical fiber. The index difference at a given point between the core and cladding is determined to better than 1 part in 10(5), implying a precision in the profile parameter alpha of +/-0.005, an order of magnitude better than existing techniques.     

Theoretical analysis for the influence of the core radius on long period fiber grating sensors

Abstract

The influence of core radius on refractive index sensitivity of long period fiber grating (LPFG) sensor has been studied theoretically for the first time, and a new method to fabricate LPFG sensor with high sensitivity is proposed. The structure and parameters of the optical fiber, the period of the gratings, and the coupling order of the cladding modes are all held consistent in the process of studying the change of the core radius. The resonant wavelength of LPFG sensor shifts with changes in the external environment, which is simulated by the transfer matrix method. The sensitivity of LPFG sensor is enhanced by more than 200 times when the core radius increases from 3.1 to 5.1?μm. The results show that LPFG sensors with larger core radii have higher sensitivity. Selecting a fiber with a large core radius to fabricate LPFG sensors is proposed as a method to improve the sensitivity of these devices. This new simple and effective method is expected to be widely used in the manufacture of high sensitivity LPFG sensors in the future.