基于平均周期图法提高光纤光栅微弱振动信号检测能力的研究

光纤布拉格光栅(FBG)用于微弱振动检测时,当被测振动太微弱时系统输出传感信号的信噪比小于1,从时域采集的数据很难直接测得到信号的幅度和频率信息。提出一种信号处理方法,即将传感器在时域测量获得的连续数据分段后,对每段数据分别进行快速傅里叶变换获得其对应的功率谱信号,然后将频域信号做叠加平均得到新的数据。实验结果表明,采用这种频域叠加平均的方法处理后,FBG传感信号在频域内的信噪比提高了15.6dB,明显提升了微弱信号的检测能力。初步实验表明:该系统对FBG波长变化的检测灵敏度可提高到1.5fm。该信号处理方法特别适合噪声环境恶劣、被测信号以一定频率持续存在的工程应用领域,对实际环境下微小振动的识别与检测具有较大的意义。国家自然科学基金(61077031

Fiber Bragg Grating AC Current Measurement Based on Twin-Core Fiber Filter

中文摘要:利用光纤光栅( Fiber Bragg grating ,简称 FBG) 、 超磁致伸缩材料( Giant magnetost riction material ,简称 GMM)和基于双芯光纤滤波器的解调系统实现了交流电流的测量。在介绍超磁致伸缩材料的磁致伸缩效应、 光纤光栅检测电流原理以及双芯光纤滤波器解调原理的基础上 ,借助超磁致伸缩材料和光纤光栅等构建了电流测量单元。利用设计的电流测量单元 ,在施加 0～4. 5 A (50 Hz)范围的交流激励电流时 ,经基于双芯光纤滤波器的解调系统解调 ,验证了采用该方案检测电流的可行性。 英文摘要：基金项目:国家自然科学基金项目资助(60472025

电器产品塑料部件成份比对的拉曼光谱分析方法

文章通过对三种塑料样品ABS、PP、PC的拉曼光谱进行分析和比较,根据光谱的相似度算法定量计算相关的特征参数,从而区分开这三种样品。我们采用自适应迭代重加权惩罚最小二乘法（air-PLS）对2002000cm-1波段的原始光谱进行预处理,并分别采用夹角余弦法和广义Jaccard系数法计算测量样品的相似度,显示两种计算方法在判别相同和不同样品的相似性上各有优势。研究表明采用激光拉曼光谱技术结合相似性分析可以鉴别ABS、PP、PC三种塑料样品成份的差别

Gain Flattening Filter with Twin-Core Fiber

对现有放大自发辐射(ASE)光源与掺铒光纤放大器(EdfA)增益平坦的方法做了分析和讨论,采用双芯光纤和光纤波分复用(WdM)耦合器组合的方法设计了一种新的增益平坦滤波器。由于双芯光纤的传输谱特性可以通过弯曲、扭转以及拉伸等方式调节,从而这种全光纤的增益平坦滤波器具有实现简便、可调谐性好等优点,平坦化后的出射光谱在1527.36--1561.04 nM的带宽内只有±0.5 db的起伏。结果表明,采用双芯光纤与其他器件一同制作的滤波器,在光通信与光纤传感领域有较大的应用前景。Methods related to the design of gain flattening filters for amplified spontaneous emission(ASE) and erbium-doped fiber amplifier(EDFA) are reviewed.A novel scheme to realize the gain flattening filter by using a piece of twin-core fiber and a wavelength division multiplexing(WDM) coupler is proposed and verified experimentally.The spectrum of the twin-core fiber can be adjusted by bending,twisting and stretching to meet the filter requirement.The flexibility and tunable properties make the proposed all-fiber device a good candidate for gain flattening filter.The experimental results show that the ASE spectrum can be flattened in the wavelength region of 1527.36～1561.04 nm with ripples within ±0.5 dB.The results show the filters with twin-core fiber may offer great potential for optical communications and sensing applications

Design and Analysis of the High-Order Mode Dispersion Compensating Fiber

We discussed how to design the typical trip-clad high-order mode fiber (HOMF) profiles to achieve the required dispersion properties based on LP(02) mode, to compensate all modern transmission fibers, without sacrificing other important properties, such as effective area. Finally, HOMF compensating 100km eLEAF (R) fiber has been designed. Its dispersion at 1550nm is -1217ps/nm/km, and the relative dispersion slope (RDS) is 0.02nm(-1). Only similar to 345m of HOMF is needed to achieve full dispersion and dispersion slope compensation of the span, while maintaining effective area above 52 mu m(2) over the entire C-band

基于模糊理论和AHP的高速列车端部舱设计方案评价

为了使企业在面对多种结构相似的设计方案,能做出正确,合理的选择,提出了基于模糊理论和层次分析法的某型动车组端部舱设计方案的评价研究.为辅助工程师进行设计方案的选择,在综合考虑制造成本、强度、抗疲劳性能的基础上,构建了设计方案的综合评价指标体系;借助模糊数学理论,利用中值法确定评价因素与评价集的隶属度,利用层次分析法确定因素权重,对动车组端部舱三种设计方案分别进行模糊综合评价,从中获得最优设计方案.实践表明,所建立的评价体系可以快速获得客观综合评价结果,能为企业设计方案的择优选择提供依据.国家自然科学基金资助项目(51220001);中国铁道总公司科技研究开发计划资助项目(2013J012-B);大连市科技计划资助项目(2011D11ZC093

基于D型光纤Bragg光栅的加速度传感器

本文介绍了一种新型的基于d型光纤brAgg光栅(d-fbg)测量加速度信号的方案,并对测量系统进行了理论分析和实验测量。该加速度传感器具有尺寸小、质量轻、结构简单、灵敏度高等优点,可用于测量低频振动(0.1Hz数量级)和小幅值的加速度信号。试验数据表明基于该方案的测量灵敏度可达到563.67με/g,最小分辨力为1.15x10-3g

Research on Fiber Gas Sensor System Based on Scanning Light Source

提出了一种基于窄带扫描光源的光纤气体传感系统。该系统能在多种气体共存环境下,完成对不同组分气体浓度的检测。克服了传统光纤气体传感系统在多种气体共存环境下需要多台光源进行检测的弊端,降低了工业化气体检测的成本。系统以放大自发辐射(ASE)光源为基础,结合锯齿波(STW)驱动的可调谐法-珀(fAbry-PErOT)滤波器形成窄带扫描光源。针对可调谐滤波器的电容特性会引起锯齿波驱动失真的现象,提出了采用并联谐振回路的方案来解决锯齿波驱动失真的问题,保障了扫描光源工作的稳定性。实验结果表明,在乙炔和氨气混合气体的环境下,本系统可以实现对不同组分气体浓度的同时检测,检测结果误差较小。An optical-fiber gas sensor system based on narrowband scanning light source is proposed.It can complete the concentration detection of various gases mixed in the environment.As usual,traditional fiber gas sensor system requires multiple light sources for detection when there are several different kinds of gases.By using scanning light source,the cost of industrialization gas detection can be reduced.Using an Amplified Spontaneous Emission(ASE) source as foundmental instrument,combining tunable Fabry-Perot filter driven by saw-tooth wave(STW),narrowband scanning light is generated.As the Fabry-Perot tunable filter is a capacitive device,it can cause the linear distortion of the saw-tooth wave.Parallel resonant circuit solutions are proposed to decrease saw-tooth wave linear distortion,thus the stability of light source scanning work is guaranteed.Experimental results show that the system can detect the gas concentration of different components which are mixed with acetylene and ammonia gas.Experimental results also show low error rate.国家自然科学基金(61077031);厦门大学985与211工程资助课

Research on fiber gas sensor system based on average filtering algorithm

数字平均滤波是信号处理中一种常用的方法。在小信号检测中,使用数字平均滤波可以获得较高的信噪比,提高检测的灵敏度。本文提出了一种利用光学器件来实现数字平均滤波的新方法,应用于基于差分吸收检测原理的窄带扫描光源光纤气体传感系统。系统的输出是一段连续的光谱,包含有被测乙炔气体的多个特征吸收峰。系统使用法珀标准具ETAlOn和参考光栅提供波长参考,完成对输出信号的光谱重建。对相同波长范围的信号进行平均滤波,使气体的相同特征吸收峰重合,提高检测的灵敏度。利用光谱重建,克服了可调谐fAbry-PErOT滤波器驱动电压和透射波长不稳定因素的影响。实验结果表明,本系统可以方便有效地实现光谱意义上的数字平均滤波,检测到较低浓度的乙炔气体,比较适用于工业化气体检测系统。Digital average filtering is a widely used signal processing method.In small signal detection,digital average filtering can obtain higher signal-to-noise ratio and can improve the detection sensitivity.This paper puts forward a new method using optical device to realize the digital average filtering.Basing on difference absorption principle,a new optical fiber gas sensor system based on a scanning light source is presented,and a novel optical gas sensor system is designed.By utilizing ETALON and reference grating,it can provide reference wavelength,and realize the spectrum reproducing of the output signal.Therefore,the same spectral signals can be superposed.This method is able to overcome the uncertainty effect caused by the transmission wavelength of tunable Fabry-Perot filter and filter′s driving voltage.Experimental results show that the gas detection sensitivity is remarkably improved and can detect fairy low concentration acetylene gas.The system is suitable for industrial gas monitoring.国家自然科学基金项目(No.61077031);厦门大学“985”与“211”工程项目资

A tunable polarization-independent comb filter based on high-order mode fiber

National Natural Science Foundation of China [61077031]This paper presents an all-fiber tunable comb filter based on high-order mode fiber (HOMF). The filter is constructed by splicing a segment of HOMF between two sections of conventional single-mode fibers (SMFs), with an intentionally introduced offset at the first joint between the SMF and HOMF, and without an offset at the second joint between the HOMF and SMF, to optimize the visibility of the transmission spectrum. The optimal transverse offset of the fibers at the first joint and the tunable polarization-independent properties of the filter were studied theoretically and experimentally. An example of using this tunable comb filter in the application of a sensor, based on demodulating the wavelength shift of a fiber Bragg grating, has also been demonstrated. The particular advantages of this all-fiber tunable filter make it valuable in various applications