应用平衡双光纤光栅动态解调技术测量应力的研究

报道了一种基于解调技术使用双光纤光栅测量张力的方法。在外界拉力下一个光纤布拉格光栅反射波长的漂移被转变成从另一个被压电陶瓷片调制的光栅反射的光脉冲间隔的变化。实验表明，当测量一个40N以内的力时，测量精度可达到2．5mN。     

光纤光栅双折射效应的实验研究

本文对均匀光纤光栅和线性啁啾光纤光栅的双折射效应分别进行了实验研究. 利用压电陶瓷的压电效应实施对均匀光纤光栅和线性啁啾光纤光栅的侧向挤压, 使之产生双折射, 通过改变施加在压电陶瓷上的电压值, 可以实现对光纤光栅双折射大小的控制. 侧向挤压线性啁啾光纤光栅可以补偿光纤通信系统中的偏振模色散.     

动态匹配光栅解调传感系统温度补偿研究

采用一对辅助匹配光纤光栅,结合基于MAX1968EUI芯片闭环自动控制,设计了一种半导体小型温度控制系统.通过控制传感光栅反射峰值变化,使匹配光栅温度变化与传感光栅周围环境温度变化相匹配,实现了动态匹配光栅解调方案的应变测量系统温度补偿,消除了光纤光栅传感器温度、应变交叉敏感效应对传感系统测量应变的影响.解调系统同时采用一支微测力传感器作为解调系统的输出,消除了传统动态匹配光栅解调系统中压电陶瓷磁滞效应对测量结果的影响.实验结果表明,温度变化对系统应变测量影响误差小于2％,传感系统的线性优于0.999 5.     

基于光栅投影的轮廓测量改进方法

传统傅里叶变换轮廓方法(FTP)在测量表面突变的物体时,受物体高度变化所引起的非截断相位变化的影响,相位难以正确展开。利用双频光栅投影可以解决这一问题。在总结了传统测量方法与双频光栅测量方法的基础上,提出采用彩色复合光栅投影的测量方法。该方法只需一次采集,就能消除图像背景分量与高次分量对测量的影响,在扩大测量范围的同时可达到双频技术测量突变效果。最后,对3种方法的实际测量结果作了对比分析,证明彩色复合光栅投影方法得到的测量精度最高。     

用光纤光栅传感器研究压电陶瓷的特性

提出了一种利用光纤光栅传感器研究压电陶瓷特性的新方法.该方法采用非平衡Michelson扫描干涉仪对光纤光栅传感信号进行相位解调,通过观测波长漂移引起的相移,从而获得压电陶瓷的位移量与所加电压间的关系.实验分析了迟滞特性和蠕变现象,得到了压电陶瓷的电压-位移特性曲线以及蠕变特性曲线.实验表明,光源功率的波动对压电陶瓷迟...     

用光纤光栅传感器研究压电陶瓷的特性

提出了一种利用光纤光栅传感器研究压电陶瓷特性的新方法.该方法采用非平衡Michelson扫描干涉仪对光纤光栅传感信号进行相位解调,通过观测波长漂移引起的相移,从而获得压电陶瓷的位移量与所加电压间的关系.实验分析了迟滞特性和蠕变现象,得到了压电陶瓷的电压-位移特性曲线以及蠕变特性曲线.实验表明,光源功率的波动对压电陶瓷迟滞特性不能造成影响且压电陶瓷的蠕变特性与电压方向无关.     

双频光栅轮廓术的研究

在投影栅相位法轮廓检测中,当物体含突变部分时,包裹相位很难准确恢复,对此可用双频变精度技术来解决。如果用两种不同频率光栅分两次进行测量,无疑增加了测量负担,也无法满足实时检测的要求。提出用软件生成两种不同频率成分的复合正弦光栅,用液晶投影仪投影,针对不同物体具体突变部分的情况,可灵活生成各种不同灵敏度的复合光栅。只采一次图像就可以达到以往双频技术中多次采集的效果,该法具有快速和去包裹精度高的特点。最后,进行了实验测试,结果非常满意。     

压电陶瓷驱动的动态匹配光栅滤波解调法优化

提出并实验验证了一种动态匹配光栅滤波系统的优化解调方法.在压电陶瓷驱动的动态匹配(光纤)光栅滤波解调系统中,一方面采用上升高压锯齿波,以消除压电陶瓷滞回效应;另一方面将压电陶瓷电压与伸长量关系的反函数作为锯齿波上升电压,以校正压电陶瓷的非线性;进而,为实现解调系统的温度补偿,引入一根中心波长保持不变的参考(光纤)光栅.在锯齿波上升过程中,匹配光栅与参考光栅和传感(光纤)光栅在不同时刻匹配,匹配时间差仅与传感光栅有关,而与解调系统温度无关.实验结果表明,优化后系统的线性度可提高2%,灵敏度与理论值的相对误差小于0.6%;在10～60℃范围内,该解调系统温度变化引起的相对误差小于1%.     

一种基于光纤光栅法布里-珀罗腔的低频振动传感器

提出了一种基于光纤光栅法布里-珀罗(F-P)腔的低频振动传感方案并进行了理论分析和实验研究。采用单频激光器作为光源,光纤光栅F-P腔通过两点涂胶方式粘接在等强度悬臂梁上,待测振动信号通过支架和悬臂梁将振动作用传至光纤光栅F-P腔,引起腔长周期性变化,从而改变光纤光栅F-P腔的反射光谱特性,通过解调输出光信号的振荡频率和峰值,即可实现对振动信号频率和幅值的测量。利用压电陶瓷模拟的低频振动信号进行了实验验证,测量结果与理论分析相吻合。该传感器测量灵敏度高,特别适用于微弱振动信号的测量。     

全光纤傅里叶变换光谱仪的关键技术研究

研究一种基于光纤Mach-Zehnder干涉仪结构的全光纤傅里叶变换光谱仪(fiber fourier transform spectrometer, FFTS)。设计了光程调制范围可达2 cm的压电陶瓷光纤相位调制器,代替传统傅里叶变换光谱仪中的动镜产生光程扫描。实验中采用1 310 nm DFB激光器作为参考光源,对测试光干涉图进行等光程间隔采样,以消除压电陶瓷非线性光程调制产生的误差。通过对测试光干涉图做傅里叶逆变换得到测试光光谱图。利用该FFTS系统测量了ASE宽带光源的光谱,并将测量结果和光栅光谱仪测量结果进行了对比,结果表明两者所测ASE光谱线型一致。最后,利用光纤光栅作为样品,对FFTS系统的光谱分辨率进行了检测,光谱分辨率达到了0.78 cm-1。     

Apodized grating coupler using fully-etched nanostructures

A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating grooves of the grating couplers are realized by columns of fully etched nanostructures, which are utilized to digitally tailor the effective refractive index of each groove in order to obtain the Gaussian-like output diffractive mode and then enhance the coupling efficiency.Compared with that of the uniform grating coupler, the coupling efficiency of the apodized grating coupler is increased by 4.3% and 5.7%, respectively, for the nanoholes and nanorectangles as refractive index tunes layer.     

Stable dual-wavelength erbium-doped fiber ring laser with switchable spacing employing controllable channel loss

A stable dual-wavelength erbium-doped fiber ring laser with switchable spacing is proposed and experimentally demonstrated. An arrayed waveguide grating (AWG) incorporating two fiber optic switches (OS) is used to as the wavelength selector. The ring cavity is divided into two cavities by a 30:70 optical coupler. Equalized dual-wavelength outputs are achieved by controlling the variable optical attenuator (VOA) inserted in the lower loss cavity. The wavelength spacing can be tuned from 0.80 to 12.05 nm. The fiber laser has good optical quality with maximum power fluctuation of 1.5 dB and side mode suppression ratios (SMSRs) higher than 71 dB.     

The Coupled-mode Theory of Grating-assisted Parallel Optical Fiber Cores

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The Coupled-mode Theory of Grating-assisted Parallel Optical Fiber Cores

A new coupled-mode formulation is developed for grating-assisted parallel optical fiber cores. The theory is derived from the scalar wave equation by perturbation method. The diffraction caused by grating and coupler in the grating region are both considered. Based on the theory, various experimental phenomena in grating-assisted parallel optical fiber cores can be simulated accurately.     

用3×3耦合器的干涉仪直接解调光纤光栅传感器的信号

为了简单直接地解调出光纤光栅的波长移动 ,提出了另外一种非平衡马赫曾德尔干涉仪的直接解调技术。用一只 2× 2耦合器和一只 3× 3耦合器组成非平衡的马赫曾德尔光纤干涉仪 ,作为光纤光栅的波长移动解调器。解调器输出的 3路信号 ,互成 12 0°相位差。通过对 3路输出信号计算的方法 ,就可以直接解调出光纤光栅的波长移动。将 3路信号采集送入计算机 ,用软件实现了信号的解调。测量结果表明 ,在干涉仪两臂长度相关 5mm时 ,测量动态应变的分辨率达到了 0 5 1nε/Hz1/2 。还得到了输出信号的频谱和输入输出信号的关系。     

对称结构光纤光栅耦合器及其应用

光纤光栅耦合器(FGC)具有光纤光栅良好的波长选择特性和光纤耦合器的多端口特点，易于实现全光纤的光波分插复用。光纤光栅耦合器主要有4种结构：基于M Z干涉仪的分离型、基于100％耦合器的非对称型、基于0耦合器的非对称型和基于100％耦合器的对称型。着重介绍对称结构光纤光栅耦合器的结构、工作原理和研究现状。提出了测试方案，并探讨了这种器件在大规模波分复用光纤传感器阵列中的应用。     

Interrogation technique for a fiber Bragg grating sensing array based on a Sagnac interferometer and an acousto-optic modulator

We propose and experimentally demonstrate a novel real-time interrogation technique for a fiber Bragg grating (FBG) sensing system that is based on a frequency-shifted asymmetric Sagnac interferometer. FBG sensors are connected to the Sagnac loop by an optical coupler, and an acousto-optic modulator (AOM) is asymmetrically placed in the Sagnac loop. By linearly sweeping the driving frequency of the AOM, the environmental variation around each FBG sensor can be determined by measuring the spectrum of the interference signals of the two counterpropagating light beams reflected by the corresponding FBG. The system has the advantages of low cost and real-time sensing.     

Fiber optic liquid leak detection technique with an ultrasonic actuator and a fiber Bragg grating

We present a technique for liquid leak detection in which ultrasonic and optical waves are introduced into a fiber simultaneously. The system is based on an ultrasonic technique using an ultrasonic actuator and a fiber Bragg grating receiver. A fiber-guided ultrasonic wave is utilized to stress the fiber Bragg grating, which is remote from the ultrasonic transmitter. When the traveling ultrasonic wave encounters a liquid, part of the wave will leak out from the fiber, which results in an ultrasonic strain decrease in the fiber Bragg grating. The ultrasonic wave and its attenuation are detected by the light variation of a narrowband laser source reflected and transmitted from the fiber Bragg grating, and the amplitude variation of the ultrasound can eventually be correlated with the fiber area coupled with the liquid.     

Demonstration of an all-optical switching operation using an optical fiber grating coupler

An optical fiber grating coupler (FGC) is a fused optical fiber coupler with a tapered region in which refractive index-modulated gratings are written. In the FGC, the light with specific wavelength satisfying the Bragg condition of the grating can be dropped to one output port and other lights are transmitted to another output port when lights with various wavelengths are launched into the input port. The FGC can operate as an all-optical switch by controlling the Bragg wavelength of the grating using a third order nonlinear optical effect caused by a control light that are launched with a signal light. In this paper, an all-optical switching operation due to a third order nonlinear optical effect in an FGC is first demonstrated for a signal light with 1.55 μm-wavelength to be changed from one port of the FGC to another one by the 720 W peak of a control light from a Nd:YAG laser with 1.06 μm-wavelength. The switching efficiency obtained was 7%. It was clarified that a longer pulse length of the control light compared to the grating length is required to obtain a large Bragg wavelength shift for the switching. It was also clarified that the Bragg wavelength shift is caused by a third order nonlinear effect and a photothermal effect. A contribution of the photothermal effect was estimated. We also estimated the switching efficiency for pump power in the FGC switch.