Bragg光纤光栅法布里-珀罗传感器的应变测量

提出了一种对静态应变进行高分辨率测量的方法。该方法是把Bragg光纤光栅(FBG)与全光纤法布里_珀罗传感器(FFPI)组合起来,利用FBG反射波长的漂移特性来测量干涉条纹的数目。通过利用FFPI和伪外差解调法对小数条纹进行解调,可实现高分辨率的测量。结果表明,静态应变的测量分辨率达到了33×10-9ε(ε为应变)。     

岩层变形检测的光纤光栅多点传感理论与工程应用

为了监测松散地层沉降变形,提出了一种用于钻孔中植入式光纤Bragg光栅传感器(FBG)的结构和传感网络系统.基于室内实验结果,给出了用于岩层变形检测的传感光栅波长带宽为6 nm,分析了多点传感信号分辨因子,山光源带宽决定的测试系统最大实际复用能力为6个传感器.设计并实现了一个由18个光纤光栅组成的具有特色的光纤Bragg光栅波分复用/空分复用混合阵列.工程实践表明,光纤光栅传感系统采用双同路布置.可提高系统下放后光纤光栅传感器的成活率.     

A Distributed Fibre Bragg Grating Sensor Interrogator Employing a Reformative Arrayed Waveguide Grating

We present an interrogating technique employing a reformative arrayed waveguide grating without output waveguides in combination with a linear charge coupled device. A simple and effective data processing method called area equalized point is used to improve the system resolution. The simulation results show that the wavelength shift of a fibre Bragg grating with temperature can be precisely measured by this interrogation technique. The temperature accuracy and wavelength resolution of the sensor system are smaller than 0.08℃ and 0.8pm, respectively. If the FBG 3dB-bandwidth is 0.2nm with the wavelength spacing between two adjacent FBGs of 1.4 nm, the temperature and wavelength errors caused by crosstalk are respectively 0.01℃ and 0. 1 pm.     

Experimental research on a novel fiber-optic cantilever-type inclinometer

Experimental setup for tilt measurement and a novel signal detection method for demodulation of fiber Bragg grating (FBG) wavelength shift are proposed. Being attached, respectively, on the upper and lower surface of only one single pendulum-type cantilever element, only a couple of matched FBGs are used for both tilt angle sensing and wavelength shift signal demodulating. So the received light power will change due to the split of the two reflected spectra of FBGs, which corresponds to the tilt angle. In addition, the cross-sensitivity effect of FBG-based sensors will be solved automatically due to a differential signal process method. Experimental results indicate the measurement accuracy is about ± 0.03°, and measurement resolution is estimated to be about 0.002°.     

Double-ring cavity configuration of actively mode-locked multi-wavelength fiber laser with equally tunable wavelength spacing

A novel actively mode-locked multi-wavelength tunable fiber laser with equally increased or decreased wavelength spacing is presented. It is constructed using a double-ring cavity combined with an amplitude modulator and cascaded fiber Bragg gratings (FBGs). The cavity lengths for all FBGs are intrinsically identical due to the double-ring configuration, and simultaneous mode locking of multiple wavelengths is therefore achieved by applying only one mode-locking signal to the modulator. The FBGs are mounted on a organic plate with angles between adjacent gratings such that the forces applied to the FBGs have an equal force increment; thus, stretching or compressing the cascaded FBGs can achieve a wavelength tuning with equally increased or decreased wavelength spacing.This revised version was published online in March 2005. In the previous version, the published online date was missing     

用超磁致伸缩调谐光纤光栅的光分/插复用器

提出并研究了一种新型多信道切换的全光分/插复用器,它主要由光纤Bragg光栅(FBG)和一对光环行器组成.采用了一种高效的超磁致伸缩材料(GMM)使FBG产生有效的Bragg波长偏移.用控制电流来调控FBG的应变和Bragg波长偏移.用4只相同的FBG与波长叠加技术相结合,可建立能提供15种不同下路信道方式的OADM.     

弯曲光纤布拉格光栅靶式流量传感器的研究

设计了一种基于光纤布拉格光栅(FBG)的弯曲靶式流量传感器,采用COMSOL软件仿真了弯曲靶臂受力时的应变分布规律,并将两支FBGs分别粘贴于靶臂的外侧和内侧进行应力测试,仿真与实验结果表明在外力作用下靶臂外侧和内侧分别产生拉应变和压应变,FBGs反射中心波长产生红移和蓝移。同时,测试了该结构的温度特性,在20 ℃~40 ℃两支FBGs反射中心波长均与温度呈线性关系,从而可消除温度对测量结果的影响。随后搭建了弯曲靶式FBG流量传感器测量装置,在0~800 L/H范围内的测量结果表明,两支FBGs反射中心波长与水流量呈较好的线性关系,其流量灵敏度为48 L/H。     

基于宽谱光源的光纤传感波长解调系统的研究

研究制作了基于宽谱光源的光纤传感波长解调系统, 以多光纤光栅作为波长参考基准、采用可调谐光纤法布里-珀罗(F-P)滤波器作为波长扫描器件。系统中采用三次多项式拟合的方法对滤波器锯齿波的扫描电压与透射波长关系曲线进行非线性拟合, 解决可调谐光纤F-P滤波器的电压—波长非线性关系对系统测量带来的较大误差问题, 实现波长的高精度解调。采用五光纤光栅做波长参考, 单根光纤光栅传感器的解调实验结果表明：待测光纤光栅布拉格波长短期测量分辨率为3.5 pm, 长期测量稳定性为7 pm。采用该系统对光纤非本征法布里-珀罗干涉型(EFPI)应变传感器的测试结果表明, 测量应变灵敏度为2.41 nm/με, 并且应变和波长之间存在良好的线性关系, 线性相关度达到0.99991。     

Tunable fiber Bragg gratings for application in tunable fiber lasers

The resonance wavelength of the fiber Bragg gratings (FBGs) is tuned using two methods. Tunable FBGs are used as the selecting elements in the cavities of tunable lasers. An ytterbium-doped fiber laser with a wavelength tuning range of 1063–1108 nm and an output power of 6 W, a Raman fiber laser with a wavelength tuning range of 1252–1303 nm and an output power of 3 W, and an erbium-doped fiber laser with a wavelength tuning range of 1530–1580 nm are realized, and their characteristics are studied.     

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.     

Multi-point abnormal-temperature warning sensor system with?different thresholds

We propose and experimentally demonstrate a time-division-multiplexing-based (TDM-based) multi-point abnormal-temperature warning sensor system with different thresholds. A multi-channel fiber Bragg grating (FBG) serving as the wavelength selector is employed in the fiber ring laser to generate a multi-wavelength pulsed light source. The sensor array is composed of multiple uniform sensing FBGs at different positions and with different nominal wavelengths. The warning signal is obtained by only monitoring the time slot between the injected pulse and the reflected pulse. The measurement range and resolution are theoretically discussed and experimentally demonstrated.     

FBG温度传感器探头的封装设计方案

提出了一种基于FBG(布拉格光纤光栅)温度传感器封装的新设计方案。一个密闭的容器被活塞分成两部分,一部分充满水银,另一部分抽成真空,两个完全一样的布拉格光纤光栅分别安装在活塞两边。当温度发生变化时,通过水银的热胀冷缩推动活塞移动,把温度的变化通过水银热胀冷缩转换成对光纤光栅的拉力和压力。而光纤光栅和金属外壳本身的热胀冷缩对两段布拉格光栅的影响是相同的,基本上可以相互抵消,因此,消除了温度和应力交叉敏感的问题。另外,理论分析表明该布拉格光纤光栅传感头的温度灵敏度可以达到2.83×10-4/℃。     

Spectrum-profile-identification-based wavelength division multiplexing method for a fiber Bragg grating sensor

A new wavelength division multiplexing method for fiber Bragg grating(FBG) sensors based on spectrum profile identification is proposed. In this method, FBGs and tilted FBG(TFBG) sensors are cascaded in a single fiber in one sensing channel. The different spectrum profiles enable the cross-correlation method to demodulate the wavelength. Therefore, the different types of sensors can occupy the same central wavelength band. Using this method, the multiplexing capacity is optimized. Experiment results demonstrate the feasibility of this method and it is useful for applications where large numbers of FBGs are needed.     

Experimental investigation of pre-irradiation effect on radiation sensitivity of temperature sensing fiber Bragg gratings

The effect of pre-irradiation on radiation sensitivity of fiber Bragg gratings(FBGs) is verified experimentally.FBGs are fabricated in photosensitive optical fibers and single mode fibers with Ge-concentration in a range from 3 mol% to 23.37 mol% in the core.In experiments,the FBGs are subjected to twice γ-radiation exposures to a Co60 source at a dose-rate of 0.1 Gy/s up to a total dose of 50 kGy.Pre-irradiation treatment can reduce the temperature sensitivity variation of FBGs by 18.12%-35.91%,as well as Bragg wavelength shift(BWS) by 8%-27.08 %.Our research demonstrates that pre-irradiation treatment is a feasible method to improve the radiation tolerance of FBGs.     

Sensing properties of fiber Bragg gratings in small-core Ge-doped photonic crystal fibers

We report about fiber Bragg gratings (FBGs) inscribed in two different types of small-core Ge-doped photonic crystal fibers with a UV laser. Sensing properties of the FBGs were systematically investigated by means of demonstrating the responses of Bragg wavelengths to temperature, strain, bending, and transverse-loading. The Bragg wavelength of the FBGs shifts toward longer wavelengths with increasing temperature, tensile strain, and transverse-loading. Moreover, the bending and transverse-loading properties of the FBGs are sensitive to the fiber orientations. The reasonable analyses for these sensing properties also are presented.     

A linearity interrogation technique with enlarged dynamic range for fiber Bragg grating sensing

An exact linearity interrogation technique with enlarged dynamic range for fiber Bragg grating (FBG) sensor has been analyzed theoretically and demonstrated experimentally. The technique bases on two matched FBGs for receiving the reflected signal from the sensor FBG and two photodiodes (PDs) for collecting the reflected signal from the two receiver FBGs. The linear expression between the nature logarithm of the output ratio of the two PDs and Bragg wavelength of the sensor FBG is obtained on the condition that the bandwidths of the two receiver FBGs being equal to each other. The wavelength of the sensor FBG can be interrogated simply and accurately by the linearity technique according to the expression. In addition, a new tunable paralleled matched gratings interrogation scheme is proposed. The interrogation range can be enlarged and multiple FBG sensors can be interrogated simultaneously with the tunable interrogation scheme.     

Gain-Flattened Optical Limiting Amplifier Modules for Wavelength Division Multiplexing Transmission

By integration of a bidirectional erbium-doped fiber amplifier and a three-port optical circulator with several fiber Bragg gratings (FBGs), two gain-flattened optical limiting amplifier (OLA) modules are proposed and experimentally demonstrated. They rely on the use of central wavelength misalignment and bending loss methods, respectively. They can effectively cover the whole useful 1.55-mum band. Both modules can provide gain-flattening characteristics over a large input dynamic range. The FBGs integrated OLA configuration has potential application in wavelength division multiplexing lightwave communication systems.     

中心波长1080 nm的高功率光纤光栅研制与测试

介绍了基于紫外光侧写和相位掩模法制作双包层光纤光栅的工艺,制作了一对中心波长1080 nm的光纤光栅,测试光谱得到其反射谱带宽分别为2 nm和1 nm。采用自制的光纤光栅搭建了一个高功率光纤振荡器,得到最高502 W的激光输出,并测试了输出激光的光谱和光束质量。     

Switchable dual-wavelength passively mode-locked fiber ring laser using SESAM and cascaded fiber Bragg gratings

We propose and demonstrate an efficient and simple wavelength switchable dual-wavelength passively mode-locked fiber ring laser based on a semiconductor saturable absorber mirror (SESAM) and a cascaded sequence of fiber Bragg gratings (FBGs). The efficient self-starting mode-locked operation was realized with a SESAM. Dual-wavelength pulses with a wavelength spacing of 12.49 nm were obtained which was determined by the reflection peaks of the FBGs used in the experiment. In addition, by rotating the polarization controllers (PCs), the switchable dual-wavelength operation was simply achieved via exploiting wavelength-dependent loss mechanism.     

基于三角波驱动法珀可调谐滤波器的光纤光栅解调偏差校正算法

为了校正解调系统在三角波上升行程和下降行程对光纤布拉格光栅(FBG)波长解调结果出现的偏差,提出一种采样点相对位置的校正算法。将三角波2个扫描行程的FBG波峰分别映射到相应的标准具原始数据中,再对2个映射波峰在标准具光谱中的相对位置偏差进行校正,达到减小解调偏差的目的。实验采用2支不同波长的FBG进行验证,结果显示,经过校正,FBG1将三角波上下扫描行程的解调偏差从12.053 pm减小到了0.476 pm,FBG2将该解调偏差从12.101 pm减小到了0.427 pm,2支传感器的解调偏差相比校正前分别减小了25.3倍和28.3倍。