Tunable phase-shifted fiber Bragg grating based on a microchannel fabricated by a femtosecond laser

A phase-shifted fiber Bragg grating(PS-FBG) based on a microchannel was proposed and realized by combining the pointby-point scanning method with chemical etching. The PS-FBG is composed of a fiber Bragg grating(FBG) and a microchannel through the fiber core. The microchannel can introduce phase shift into the FBG. What is more important is that it exposes the fiber core to the external environment. The phase shift peak is sensitive to the liquid refractive index, and it shows a linear refractive index response wavelength and intensity sensitivity of 2.526 nm/RIU and-111 d B/RIU, respectively.Therefore, such gratings can be used as sensors or tunable filters.     

光纤光栅与受激布里渊信号的耦合特性

近年来,光纤布拉格光栅传感器与全分布式光纤传感器的融合技术受到了广泛关注,然而光纤布拉格光栅与布里渊信号之间的耦合特性鲜有报道。本文研究了光栅类型、波长、反射率及光纤的光致折射率对受激布里渊信号的影响规律,并探讨了空间分辨率对光纤布拉格光栅定位功能的影响。实验结果表明,在布里渊光时域分析系统中,光纤布拉格光栅处有尖锐的反射峰,而啁啾光栅、长周期光栅及光致折射率变化的光纤处均未出现尖锐的反射峰;光纤布拉格光栅反射率与受激布里渊散射功率谱无关;当光纤布拉格光栅的波长接近1 550 nm时,对受激布里渊频移测量的影响最大;在8 m的长度范围内,光纤布拉格光栅的定位误差约为4 cm,并且与空间分辨率无关。     

具有温度自校准功能的光纤折射率传感器

提出一种具有温度自校准功能的光纤折射率（RI）传感器,传感头结构由2段很短的多模光纤（MMF）之间夹熔一段对折射率不敏感的光纤布拉格光栅（FBG）构成,传感头总长度为14 mm,FBG可以为折射率测量提供良好的温度校准功能。实验结果证明,该传感器的折射率灵敏度为126 nm。其干涉光谱共振波长的温度灵敏度为35.09 pm/℃,用于温度校准的FBG的温度灵敏度为11.14 pm/℃。相比于普通的折射率传感器,这种具有温度自校准功能的折射率传感器具有良好的实用前景。     

Volatile organic compound sensing using a surface-relief D-shaped fiber Bragg grating and a polydimethylsiloxane layer

The authors use a surface-relief fiber Bragg grating with a polydimethylsiloxane (PDMS) layer as a volatile organic compound chemical sensor. A PDMS layer is used because it is compatible with the optical properties of the grating and exhibits good chemical selectivity. As the analyte is absorbed the refractive index of the PDMS changes, causing the Bragg wavelength to shift, and this shift is correlated to chemical type and concentration. The direction and amount of the Bragg wavelength shift is dependent on the absorbed chemical. The authors demonstrate chemical differentiation between dichloromethane and acetone in gaseous states.     

基于光纤微结构加工和敏感材料物理融合的光纤传感技术

将功能敏感材料与光纤在物理层面进行有机融合,充分发挥光纤传感器在结构集成、材料集成等方面的优势,将有望发展新型的光纤传感器件和系统.本文综述了飞秒激光光纤微加工技术分别在标准的单模光纤和光纤光栅上制备微结构,再结合敏感材料制备技术,实现在物理层面上光纤传感器材料和结构的集成和融合,探索实现新型高性能的光纤传感新技术.     

Hybrid FBG–LPG sensor for surrounding refractive index and temperature simultaneous discrimination

In this work, we propose a configuration of a hybrid fiber Bragg grating together with a long period grating sensor used for simultaneously detect surrounding refractive index and temperature to be applied in aqueous environment and to reveal pollution. We present the simulation of such sensor and analyze the reflected wavelength and amplitude variations of the fiber Bragg grating spectrum to obtain the temperature and the external refractive index variations, respectively. The results show that the fiber Bragg grating reflected amplitude change depends on the variation of the long period grating transmission spectrum with the surrounding refractive index modification and the reflected wavelength shift depends on the temperature of the aqueous solution.     

基于光纤布拉格光栅与长周期光栅并联的集成光学传感器

为了提高光纤传感器的性能和进一步缩小传感器的尺寸,通过实验制备出一种基于光纤布拉格光栅(FBG)与长周期光栅(LPG)并联的新型集成光学传感器。该传感器中的FBG和LPG是利用飞秒激光直写技术直接在普通单模光纤中刻写的。FBG和LPG是并联关系,因此很大程度地缩小了传感器的长度。外界的温度和折射率的变化会引起FBG和LPG的谐振峰波长位置发生变化,据此对该集成传感器进行温度和折射率测量。实验结果表明:FBG谐振峰对折射率和温度的灵敏度分别为0 nm/RIU和12.98 pm/℃,而LPG在1 555 nm附近谐振峰对折射率和温度的灵敏度为196.46 nm/RIU和10.93 pm/℃。因此,根据双参数传感矩阵,该传感器可以对温度和外界折射率进行同时传感。     

Rapid fabrication of microhole array structured optical fibers

A microhole array in a common single-mode fiber is fabricated by selective chemical etching of femtosecond-laser-induced fiber Bragg grating (FBG), which has a laser-modified region extending from the fiber core to the cladding-air boundary due to laser self-focusing. The shape and size of the orderly microhole on the fiber surface are controlled via changing conditions of FBG fabrication and chemical etching. A simultaneous sensing for surrounding refractive index and temperature is demonstrated by this microhole array FBG through measurement of the transmission power change and Bragg resonant wavelength shift.     

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.     

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.     

基于虚拟仪器和可调谐激光技术的光纤光栅传感系统

提出了一种新颖的基于虚拟仪器(VI)和可调谐激光技术的光纤光栅(FBG)传感系统,利用可调谐激光对由光纤光栅组成的传感器阵列进行波长扫描,实现了多根光栅的复用准静态解调,并结合抖动技术和反馈环结构,使得探测信号在每一根传感光栅中心波长处过零,以提高系统在测定波长偏移时的分辨力。当反馈环工作在闭环状态下时,该系统还可对单根光栅实现动态跟踪锁定,实现单根光栅的动态解调。该传感系统的数据采集采用虚拟仪器技术,通过多通道同时输入输出实现了在线实时解调。实验采用了4根光栅组成传感阵列,获得了静态多根光栅小于1με和单根光栅动态频率10 Hz时3.3 n/εHz的解调分辨力,动态应变范围在850με。     

On the possible use of optical fiber Bragg gratings as strain sensors for geodynamical monitoring

Optical fiber sensors can be used to measure many different parameters including strain, temperature, pressure, displacement, electrical field, refractive index, rotation, position and vibrations. Among a variety of fiber sensors, fiber Bragg gratings (FBG) have numerous advantages over other optical fiber sensors. One of the major advantages of this type of sensors is attributed to wavelength-encoded information given by the Bragg grating. Since the wavelength is an absolute parameter, signal from FBG may be processed such that its information remains immune to power fluctuations along the optical path. This inherent characteristic makes the FBG sensors very attractive for application in harsh environments, “smart structures” and on-site measurements.This paper reviews the achievements about the FBG as a strain and temperature sensor and describes the potential applications of FBG sensors for applications in the field of geophysics and its expected development in the near future. The applications could include: rock deformation, fiber-optic geophone, optical based seismograph, vertical seismic profiling and structural monitoring of civil structures. Different techniques to detect strains and various applications will be reviewed and discussed. The problem of temperature–strain cross sensitivity, that is particularly difficult to eliminate, is addressed and approaches to overcome it are discussed.     

侧面研磨光纤Bragg光栅的外部折射率敏感特性研究

光纤Bragg光栅对外界折射率的变化不灵敏,无法直接作为气体、液体等的敏感元件.侧面研磨的光纤Bragg光栅,一侧包层减小至几微米,其辐射场可通过包层透射到被传感物质,因而被传感物质的折射率的变化可以改变光纤的有效折射率,从而使光栅的Bragg波长产生位移.实验中利用不同浓度的NaCl溶液来改变光纤光栅的外部折射率,Bragg中心波长的偏移量和浓度近似为线性关系.同时,透射功率的变化量和浓度也近似为线性关系.     

优化光纤光栅传感器匹配光栅解调方法的研究

利用悬臂梁调谐和两个并联二次反射匹配解调光栅的方法实现了光纤布喇格光栅(FBG)传感器的高精度大范围应变传感测量.通过并联方式,选择合适的匹配光栅波长,增大了可检测的应变范围,同时解决了双值问题.应变传感信号经两路解调光栅解调,并由数据采集卡采集后,由计算机进行两路并联信号的综合处理后获取更准确的结果,使得系统性能得到提升和优化.试验结果与理论分析一致.     

基于光纤布拉格光栅传感器的光纤光栅智能夹层试验研究

传感元件与复合材料的一体化是智能结构研究的最终目标之一。设计一种具有自诊断功能的标准化、模块化光纤智能夹层系统,正是实现这种一体化最有潜力的技术途径。采用聚酰亚胺薄膜制作了基于光纤布拉格光栅（FBG）传感器的光纤光栅智能夹层,对智能夹层中光纤布拉格光栅传感器的应变、温度特性进行了标定试验,并建立了基于光纤布拉格光栅传感器光纤光栅智能夹层的应变、温度测量模型。试验表明,智能夹层内布拉格光栅波长偏移与应变、温度之间具有良好的线性关系。不过在温度测量时,必须考虑被埋人结构的热膨胀效应。利用光纤光栅智能夹层内光纤布拉格光栅传感器网络和先进信息处理技术,可以建立结构损伤主动、在线和实时监测系统。     

A novel fiber Bragg grating interrogating sensor system based on AWG demultiplexing

A fiber Bragg grating (FBG) interrogating technique based on the relative intensity-demodulating and the demultiplexing of an arrayed waveguide grating (AWG) is presented in this paper. The analytical simulation and the experiment validate the feasibility of this setup. Both theoretical and experiment results show that the shift of the Bragg wavelength of the FBG sensors can be precisely interrogated by the relative intensity reading of two-adjacent-channels of the AWG-based demultiplexer. Errors caused by the light source fluctuation and micro-band losses can be reduced with the relative technique. This technique potentially offers a low-cost, compact, and high-performance solution for the interrogation of FBG distributed sensors.     

基于线阵InGaAs光电二极管阵列的光纤光栅传感解调

采用线阵InGaAs光电二极管阵列和体相位光栅并结合空分复用和波分复用技术,对光纤光栅传感进行解调.设计了基于线阵InGaAs光电二极管阵列和体相位光栅的光纤光栅传感解调系统,通过系统测试和性能分析,该解调系统解调带宽42 nm,信噪比30 dB,波长偏移测量精确度±15 pm,功率测量精确度为±0.3 dB.基于线阵InGaAs光电二极管阵列和体相位光栅的光纤光栅解调系统不但尺寸小,功耗低,而且具有较高的解调速度.     

Numerical analysis of plasmon polarition refractive index fiber sensors with hollow core and a long period grating

The main principle of this design is based on the efficient energy transfer between the waveguide mode (WM) and the co-directional SPP provided by a properly designed fiber long period grating (LPG). This LPG is imprinted into a waveguide fiber layer of a specially designed hollow core optical fiber. The simulations are based on the finite element method (FEM) algorithm in electromagnetics and coupled mode theory for gratings. Compared to the previous proposed structure using a fiber Bragg grating (FBG), this novel kind of sensor can greatly enhance the refractive index sensitivity, e.g., from 5.93 nm/RIU (with FBG) to 817 nm/RIU (with LPG) at the sensing refractive index of 1.40. The other advantage is that the working conditions can be performed for the well-developed telecom wavelength windows 1500-1600 nm.     

可分离温度影响的FBG应变测量方法

光纤布拉格光栅在通信和传感领域具有广泛的应用。利用光纤布拉格光栅中心波长的偏移，可以测量温度和应变等多种物理量，但必须解决光栅对温度和应变的交叉敏感问题。该文简要分析了光纤光栅作为传感器的基本原理及其优点，设计了利用参考光栅法分离温度影响以及利用掺铒光纤的自发发射放大特性分离温度影响的2种应变测量方法。最后，介绍了一种利用倾斜光纤光栅的主模和边模对布拉格光栅中心波长的偏移进行解调的方法，该方法成功地分离了温度对应变测量的影响。     

Simultaneous measurement of refractive index and temperature using dual-period grapefruit microstructured fiber grating

By cascading the long period fiber grating (LPFG) and fiber Bragg grating (FBG) in grapefruit microstructured fiber, a novel dual-period fiber grating sensor is proposed. The refractive index and temperature are measured simultaneously by using the different sensitivity of FBG and LPFG. The relationship between dual-period fiber grating transmission spectrum and refractive index, resonant wavelengths and temperature are analyzed theoretically, respectively. The simulation results show that the accuracy of the sensor in measuring refractive index and temperature is estimated to be 2319.6 nm/RIU in a range from 1.33 to 1.36 and 0.017 nm/°C from 0 °C to 100 °C, respectively. Thus, the sensor has high refractive index sensitivity, and can provide the theoretical foundation for the optical fiber biosensor.