Optical Fiber Sensor Technology in Portugal

A general overview of the R&D activity in fiber optic sensing developed over the last fifteen years in Portugal is given. Different topics are addressed, including interferometric, intensity and Bragg grating based fiber optic sensors, signal processing and multiplexing techniques, optical current sensors, together with some references to field trials and applications. Possible guidelines for present and future national R&D activity on this subject are outlined.     

Fabrication of Optical Fiber Devices

In this paper we present the main research activities of the Laboratorio de Fibras Opticas del Instituto de Ciencia de los Materiales de la Universidad de Valencia. We show some of the main results obtained for devices based on tapered fibers, fiber Bragg gratings, acousto-optic effects and photonic crystal fibers.     

Fabrication of Optical Fiber Devices

In this paper we present the main research activities of the Laboratorio de Fibras Opticas del Instituto de Ciencia de los Materiales de la Universidad de Valencia. We show some of the main results obtained for devices based on tapered fibers, fiber Bragg gratings, acousto-optic effects and photonic crystal fibers.     

Multiplexed Optical Fiber Interferometric Sensor System by Synthesis of Optical Coherence Function with Phase Generated Carrier

A novel system for multiplexed optical fiber interferometric sensors is proposed applying the synthesis of optical coherence function with phase generated carriers. The ideal parameters of the laser diode frequency modulation for the phase generated carrier with the synthesis of the optical coherence function are discussed. A basic experimental setup including two interferometric sensors is constructed. The results show that the phase signal from the two sensors can successfully be demultiplexed by scanning the synthesized coherence peak.     

Applications of Fiber Optic Grating Technology to Multi-Parameter Measurement

In this article, approaches reported in the literature for multi-parameter measurement relying on fiber grating technology are reviewed. Due to its importance, the particular case of temperature/strain simultaneous measurement is addressed in further detail, as well as the techniques and sensing heads for temperature-independent strain measurement. Specific criteria are also proposed for sensing head classification in the context of multi-parameter measurement.     

Applications of Fiber Optic Grating Technology to Multi-Parameter Measurement

Abstract

In this article, approaches reported in the literature for multi-parameter measurement relying on fiber grating technology are reviewed. Due to its importance, the particular case of temperature/strain simultaneous measurement is addressed in further detail, as well as the techniques and sensing heads for temperature-independent strain measurement. Specific criteria are also proposed for sensing head classification in the context of multi-parameter measurement.     

阵列波导光栅解调的准分布式光纤光栅传感器

从理论上和实验上研究了一种操作简单、响应速度快,价格低廉和高分辨率的基于阵列波导光栅(AWG)的准分布式光纤布拉格光栅(FBG)传感器.该传感系统采用了阵列波导光栅双通道强度解调技术对光纤光栅的布拉格波长和温度进行精确的解调.实验结果表明,该系统对宽带宽光纤光栅的布拉格波长和温度解调均具有高线性度,考虑系统稳定性及光纤布拉格光栅之间的串扰影响,波长测量精度仍可达2 pm,温度测量精度优于0.2℃.     

长周期光纤光栅扭曲传感器

发现用高频CO2激光写入的长周期光纤光栅的谐振波长会随光栅扭曲而线性变化。当顺时针扭曲时，谐振波长向长波方向漂移；逆时针扭曲时，谐振波长向短波方向漂移。该新型扭曲传感器不但能实现对扭曲率的直接测量，而且能判断扭曲方向，因此具有广泛的应用前景。     

光纤光栅水位传感器的理论模拟与实验研究

研制了一种光纤光栅水位传感器.采用三维有限单元法,对传感器的结构型式进行优化分析,得到水位与光纤光栅中心反射波长之间光 力转换的线性关系;制作了传感器模型,对模型的光 力转换关系进行了测试,实验结果与理论结果基本一致.该传感器经多次改进,通过试用,可用于工程检测.     

基于光纤激光器的波分复用光纤光栅传感系统

用传感器光栅串作环形腔激光器的端镜 ,借助腔镜倾角可调法布里珀罗滤波器对波分复用传感元进行波长寻址 ,利用非平衡迈克耳孙扫描干涉仪对来自传感光栅的包含应变信息的波长漂移信号进行解调 ,实验证实系统的应变传感灵敏度为 1 6 6 9°/ με ,与理论值 1 6 78°/ με非常吻合。锁定来自某一光栅的信号后 ,所设计的反馈装置保证了系统具备自动追踪感测信号的能力。     

强度调制型光纤传感器的补偿技术

采用光桥平衡技术可实现对强度调制型光纤传感器系统不稳定因素的补偿。文中给出透射式和反射式两种改进方案，对其进行了较详细地分析，提出的反射式光桥补偿的结构具有简单，可靠，实用的特点，实验结果与理论分析相一致，取得较好的补偿效果。     

基于光纤环形激光器和光放大的100 km光纤布拉格光栅传感系统

在基于掺铒光纤-拉曼混合放大的可调光纤环形激光器的光纤布拉格光栅(FBG)传感系统结构基础上,提出了延长传感距离的新方法。该方法以环形掺铒光纤激光器作为光源,采用双波长拉曼放大的方法对信号进行低噪声的双向放大,系统中间的两段掺铒光纤再利用剩余的抽运功率产生自发辐射光和放大传感信号,使得整个系统能够在超长的传感距离上获得很高的信噪比。实验表明使用一只40 mW的掺铒光纤放大(EDFA)抽运源、一只170 mW的拉曼抽运源和一只2 W的拉曼抽运源,可以使整个系统的传感距离达到100km,并且传感系统的光纤布拉格光栅反射信号均能获得超过57 dB的优良信噪比,从而实现在超长距离上的光纤布拉格光栅传感。     

Underwater Acoustic Sensor with Fiber Bragg Grating

A new type of underwater acoustic sensor is proposed with an optical fiber Bragg grating (FBG). Because of the photoelasticity with respect to the refractive index and the elasticity of the fiber, the sound pressure in water modulates the Bragg reflection wavelength and, in turn, the intensity of the laser light transmitted through the FBG fiber. Good linearity between the detected signal and the sound pressure is obtained in the range from 81 dB to 140 dB re 1 μPa. Since the upper and lower limits of the acoustic signal level for operation of the sensor are limited by the driving circuit and the transduction of the sound in water, the sensor is expected to operate with much larger dynamic range both at higher and lower pressure levels. Operation of the sensor is very stable with the insertion of optical isolators into the system, although without the isolators the output signal fluctuates at low frequency due to the Fabry-Perot interference effect between the FBG and the various facets.     

光纤传感器位移和转速测量研究

介绍光纤传感器的测量原理,并对位移和转速测量进行研究,利用matlab软件对位移测量结果进行曲线拟合,且将光纤传感器和电涡流传感器的转速测量结果进行比较,最后得出利用光纤传感器进行测量具有电路结构简单、精度高、光路弯曲等优点。     

光纤光栅电流传感器

基于悬臂梁技术 ,分析并验证了光纤光栅用于电流传感的可能性。采用等腰三角形悬臂梁确保光栅在传感过程中不出现啁啾现象 ,从而减小读数误差。系统传感灵敏度为 4 0 0× 10 - 2 nm A ,与预期值 4 15× 10 - 2 nm A基本吻合。     

激光调频光纤位移传感器多路复用技术的研究

叙述了运用半导体激光器连续波调频外差干涉和频域多路复用原理，研究了光纤位移传感器多路复用技术。已研制成的分频与分幅相结合四路复用光纤位移传感器，可同时进行对多点、多维位移和多种物理量的测量，各路位移测量范围大于１ｍｍ，测量精度优于０．１μｍ及位移分辨率为０．０１μｍ。     

塑料光纤纤端光场测试结果及分析

对纤端光场进行了理论分析,分别利用塑料光纤和多模光纤作为接收光纤对塑料光纤的出射纤端光场进行了测量,并与理论分析结果进行了比较,给出了合理的调和参数.传输距离较长的塑料光纤由于高阶模的泄漏,纤端光场分布非常接近高斯分布.实验结果表明了理论分析结果和调和参数选择的合理性.     

基于干涉解调技术的光纤光栅传感系统

介绍一种基于干涉解调技术的光纤光栅传感系统 ,用非平衡波长扫描迈克耳孙干涉仪将来自传感光栅的包含应变信息的波长信号变为相位信号 ,借助相位计显示的相位变化确定待测应变的大小。该传感系统具备分辨5 .5nε的能力 ,其灵敏度的实验值为 1.80° με,与预期值 1.83° με基本吻合     

Theoretical and Experimental Study of a Code-Division Multiplexing Fiber Bragg Grating Sensor System

Abstract

A novel scheme for a code-division multiplexing based fiber Bragg grating sensor system is theoretically analyzed and experimentally demonstrated. The results show that the proposed scheme enables an improved signal-to-noise ratio performance compared with the time-division multiplexing method and that spontaneous–spontaneous beating noise should be included in the analysis to avoid overestimation. The simple and effective setup provides a competitive approach for using fiber Bragg grating sensors in practical application systems.     

A Novel Acoustic Emission Fiber Optic Sensor Based on a Single Mode Optical Fiber Coupler

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