Optical bend sensor based on measurement of resonance modesplitting of long-period fiber grating

We report an effective new method of realizing optical bend sensing based on the measurement of bending-curvature encoded resonance mode splitting of long-period fiber grating. The bending induced mode splitting exhibits a near-linear response and the bending sensitivity achieved by this method is nearly four times higher than the previously reported wavelength shift detection method. The evolution of the transmission loss under bending appears dependent on the initial mode coupling strength     

基于级联长周期光纤光栅的新颖温度传感器

设计了一种基于级联长周期光纤光栅(Long period fiber grating)的新颖温度传感器.理论上得到光栅间光纤的长度随温度增加变化时,级联LPG的干涉峰将线性地向长波方向漂移,其消光比亦将呈现线性变化.实验上制作出了基于级联LPG的光纤温度传感器.利用其某一干涉峰的中心波长和消光比测量温度变化时,测量灵敏度分别为0.0353 nm/℃和0.0684 dB/℃.基于级联长周期光纤光栅的温度传感器具有广泛的应用前景.     

Switchable dual-wavelength ytterbium-doped fiber laser based on a few-mode fiber grating

The authors propose and demonstrate a simple switchable dual-wavelength Ytterbium-doped fiber laser based on a few-mode fiber grating. The laser can be designed to operate in stable dual-wavelength or wavelength-switching modes, due to the polarization hole burning enhanced by the few-mode fiber grating. The lasing lines may be controlled only by a polarization controller. Stable operation is achieved at room temperature when the wavelength separation is 0.9 nm.     

长周期光纤光栅温度传感器的研究进展

长周期光纤光栅（LPFG）具有与短周期光纤光栅所不同的光谱特性。它无背向反射光谱,不对光源的稳定性产生影响。基于纤芯基模与包层模的谐振耦合原理和热光效应,LPFG温度传感器利用谐振波长的漂移变化实现对温度的测量,具有很高的灵敏度。介绍了LPFG的制作方法、LPFG温度传感器的工作原理及最新研究进展。由于具有插入损耗小、可用于遥测、精度高和抗电磁干扰能力强等优点,LPFG温度传感器将有广阔的应用前景。     

Periodical corrugated structure for forming sampled fiber Bragggrating and long-period fiber grating with tunable couplingstrength

A novel corrugated structure on an optical fiber is proposed and demonstrated to produce tunable long-period index modulation based on photoelastic effect. The corrugated structure is a periodic variation made by chemical etching on the cladding radius of an optical fiber. By imposing this corrugated structure upon a built-in fiber Bragg grating (FBG), a superstructure grating with tunable reflectance is formed. In addition, couplings between the fundamental core mode and cladding modes take place under such a corrugated structure when the phase-matching condition is satisfied. Thus, the device can also act effectively as a long-period fiber grating (LPFG) with tunable coupling strength. We also develop the coupled-mode theory based on Fourier series expansion to describe such a corrugated sampled Bragg grating. The phase-matching condition for various sampling orders can be derived, and the calculated spectra are compared with those based on the fundamental matrix method. Optical measurements demonstrate some unique characteristics of these devices, and good qualitative agreements between simulation and measurement verify the viewpoint that long periodic index modulation is indeed induced by such a corrugated structure through the photoelastic effect when a tensile force is applied     

长周期光纤光栅构成的迈克尔逊干涉仪及其传感应用

利用高频CO2激光器刻写了性能优良的长周期光纤光栅,然后在长周期光纤光栅近端用光纤切割刀切割出一个光滑的反射面,利用该反射面与长周期光纤光栅一起构成一个简捷的在线光纤迈克尔逊干涉仪.实验研究发现干涉仪的反射谱谐振峰波长随环境温度与轴向应变线性漂移,通过解调波长的漂移量能够测量出环境温度与轴向应变.实验获得温度灵敏度为4...     

Multiwavelength Raman fiber-ring laser based on tunable cascaded long-period fiber gratings

Multiwavelength Raman fiber lasers using intracavity tunable cascaded long-period fiber gratings (LPFGs) are discussed. The application of the cascaded LPFGs as a multichannel fiber filter for the multiple-wavelength generation is proposed and experimentally demonstrated. The characteristics of multiwavelength fiber-ring lasers can be controlled by changing the physical parameters of cascaded LPFGs such as the separation distance between the gratings, grating length, and number of gratings. The multiwavelength Raman fiber-ring laser with nine wavelength-division-multiplexing channels with 100-GHz spacing and 19 channels with 50-GHz spacing has been achieved by varying the physical parameters of cascaded LPFGs.     

A novel fiber Bragg grating sensor for weak pressure measurement based on the Stokes parameter

Unlike usual spectral analysis of the fiber Bragg grating (FBG) sensors, a novel weak pressure sensor based on the Stokes parameter of FBG is proposed in this paper. The evolution of the first normalized Stokes parameter s₁ with respect to pressure is studied theoretically and experimentally. A theoretical model for pressure sensing by use of s₁ is built and numerically simulation is also carried out. The dual-wavelength analytical method is proposed to reduce the influence of Bragg wavelength drift and improve the measurement accuracy. Under the pressure conditions of 0–5 N, the experimental pressure sensitivity is 0.0754/N. Good agreements between experiment results and numerical simulations verify the feasibility of the method.     

A wavelength- and loss-tunable band-rejection filter based oncorrugated long-period fiber grating

We demonstrate a long-period fiber grating composed of an etched corrugated structure that can be used as a wavelength- and loss-tunable band-rejection filter. The tunabilities are based on the index modulation capable of being varied in the corrugated structure under externally applied mechanical forces. The new type of fiber filter enables wavelength and loss tuning ranges of more than 30 nm and 25 dB by adjusting the applied amounts of torsion and tensile forces, respectively     

光纤光栅与法珀微腔温度应变双参量传感器

针对光纤应变传感器的温度-应变交叉敏感性问题,研究了一种结合光纤布拉格光栅(FBG)与法布里-珀罗(FP)微腔的光纤FBG-FP混合型温度应变双参量传感器.该传感器由两根垂直切割的单模光纤穿入一段石英毛细管(Glass capillary),并在石英毛细管两端固定制成,其中一根光纤端面附近预刻FBG,两根光纤端面间距为...     

基于光纤光栅传感的变压器绕组温度检测系统

传统温度传感器受到周围环境因素的影响很大,系统采用抗干扰能力强并且对温度极其灵敏的光纤光栅传感器.利用光信号的测量和传输,再解调成温度信号.分析了光纤光栅传感器的原理和系统构成,介绍了软件和硬件的实现.最后的实验结果证明了系统具有较高的测量精度,可满足变压器绕组高精度温度测量要求.     

基于膜片的光纤布拉格光栅压力传感器的研究

理论分析了光纤布拉格光栅的压力传感特性,给出了光纤布拉格光栅的中心波长与压力的关系以及压力灵敏度系数的表达式,并将光纤布拉格光栅纵向粘贴在自行设计型号为ZXYC01的平面膜片上进行了压力实验.实验结果表明光纤布拉格光栅压力灵敏度系数46 pm/MPa左右,其测量精度为0.5%F.S,而理论的压力灵敏度系数为51 pm/MPa左右,实验值和理论值基本相符,它们分别是裸光纤布拉格光栅压力灵敏度系数的23和26倍.同时发现光纤布拉格光栅的中心波长与压力变化有着良好的线性关系和很高的相关系数并且迟滞现象较小.     

在光纤拼接处刻写长周期光纤光栅及其传感应用

在"单模光纤-细芯光纤"拼接处刻写了 Type Ⅱ 型长周期光纤光栅,构成一种高温光纤传感器.该传感器实际由2 段不同的长周期光纤光栅级联构成,在第二个光栅形成了 Mach-Zehnder 干涉,因此,传感器透射谱由长周期光纤光栅与Mach-Zehnder 干涉仪共同作用形成.利用传感器的透射谱与环境温度的线性变化关系...     

基于光纤光栅的螺纹钢标准试件拉伸应变分析与测量

利用光纤光栅作为传感元件,对螺纹钢标准拉伸试验试件的拉伸应变特性进行了分析与测量,采用电阻应变片作为对比测量,并与理论值进行了比较.测量结果FBG2的应变测量灵敏度为15.647 με/kN非常接近理论期望值15.680με/kN,而电阻应变片的应变测量灵敏度仅为14.162 με/kN;同时,利用光纤光栅测量钢筋试件弹性模量,其中FBG2测得弹性模量为2.03×105MPa与标准测量值一致.结果表明,作为测量应变的常用仪器,光纤光栅比电阻应变片具有更强的实用性.     

基于光纤光栅传感器的飞行器结构健康监测

综述了光纤光栅传感器在飞行器结构健康监测中的研究现状,概述了光纤光栅传感器的工作原理和特点,研究了基于光纤光栅传感器的飞行器结构健康监测系统的组成和主要研究内容。     

High strength coupling and low polarization-dependent long-period fiber gratings based on the helicoidal structure

A compact helicoidal long-period fiber grating (HLPFG) was fabricated by twisting a single mode fiber with CO₂ laser beam exposure and its characteristic was experimentally investigated. The eccentricity between the core and the cladding of a fiber is introduced from the screw-type deformation. This helically induced significant periodic index change along the fiber produces strong mode coupling between the core and the cladding of −20 dB with a short grating length of 1 cm. The novel resonance wavelength shift of a HLPFG was analyzed with co-directional or contra-directional torsion to the helix.     

基于萨格纳克环与光栅的双波长光纤激光器

报道一种基于保偏光纤的萨格纳克环与级联的光纤布拉格光栅的双波长掺铒光纤激光器,该激光器采用简单的线性腔结构,所用的萨格纳克环担当了梳状滤波器,光栅组构成了波长选择器件;在偏振烧孔的作用下,通过调整偏振控制器,激光器能够输出5种不同的激发模式,其中,双波长2种,单波长3种;所有的激发线具有小于0.3nm线宽,大于24dB的光学信噪比;同时,该激光器展示了较好的波长与峰值功率稳定性.     

磁光纤光栅传感器灵敏度及动态范围研究

利用传输矩阵的方法,研究了在线偏振光输入的情况下,磁光纤光栅的透射谱特性.透射谱中存在两条尖锐谱线,谱线的间隔随外加轴向磁场强度的大小线性变化,可以用于磁光传感.并且进一步研究了Bragg波长和一级磁光系数对传感器的灵敏度和动态范围的影响,为设计性能较好的磁光传感器提供了理论依据.     

Refractive index sensor based on measuring the transmission power of tilted fiber Bragg grating

A low-cost, compact and practical method to measure the surrounding refractive index (SRI) is proposed by measuring the transmission power of the tilted fiber Bragg grating (TFBG). The transmission power of the TFBG is detected when the SRI varies from 1.3723 to 1.4532; the power decreases monotonously from ?2.14 dBm to ?3.26 dBm. Under this condition, the resolution of the refractive index of TFBG is predicted to be 10^?4 and the resolution of the concentration of the solution is as slight as 0.01%. Considering its simple configuration and high stability, this way is potential to monitor physical, chemical and biological parameters in the natural environments.