光纤傅里叶变换光谱术在光纤光栅传感解调中的应用

介绍了光纤Mach-Zehnder干涉仪的基本原理和光纤傅里叶变换光谱仪(FFTS)的结构;基于光纤Mach-Zehnder干涉仪,采用傅里叶变换光谱算法对光纤Bragg光栅传感器的波长进行了解调。宽带光源发出的光经过光纤耦合器进入光纤Bragg光栅,其反射光由耦合器返回进入到FFTS中进行测量,FFTS的最高光谱分辨率达到0.05 cm-1,即在近红外1 550 nm波长处分辨率为0.012 nm。分别对光纤Bragg光栅的应变特性和温度特性进行了测量。测量显示:光纤Bragg光栅的应变灵敏度为0.833 pm/με,温度灵敏度为19.78 pm/℃。得到的结果表明FFTS系统具有高分辨率、大测量范围的特点,可满足光纤Bragg光栅传感器波长解调的需求。     

Fiber optic temperature sensor using the orbital angular momentum and gaussian beams

A fiber optic temperature sensor is reported based on the interference between the orbital angular momentum and Gaussian beams. A Mach-Zehnder interferometer was employed to convert the temperature signal to a light signal of the phase difference between the reference and measuring paths. The fiber Bragg grating is included in the fiber of the measuring path. Different from the traditional sensing of fiber Bragg gratings by wavelength interrogation, the temperature-dependent phase delay near Bragg wavelength was utilized in this design. The resolution of system was better than 0.01°C. Moreover, the sensitivity of the system was obtained across various ranges of temperature. This system has potential applications in temperature measurements that require high resolution.     

光纤光栅空分光复用传感系统的研究

介绍了一种光纤光栅空分复用传感系统,并将光纤光栅的传感特性应用于结构健康检测系统中。宽带光源发出的光波进入光栅阵列时,利用光开关选通不同光路实现FBG空分复用传感系统。系统采用等腰三角形悬臂梁调谐装置对FBG进行挠度加载,利用非平衡M-Z干涉技术对传感信息进行解调,将包含被测应变信息的FBG波长信号转变成相位信号,从而得到被测应变的大小,成功地实现了空分复用传感。该系统可用于静态应变和动态应变的检测,具有高分辨力、大测量范围的特点,其传感分辨率为7.3 nε,灵敏度的实验值为0.82°/με。     

可同时测量温度和压力的高灵敏度光纤光栅传感器

报道一种新颖的基于单个光纤布拉格光栅的传感器。该传感器将光栅的一部分封装在周围填充聚合物的金属空腔里,另一部分固定在金属柱体内。由于固定的光栅部分不受应变的影响,而封装在聚合物的光栅同时受温度和应变的影响,因此该结构可实现温度和应变的分离传感。同时,这种聚合物封装的结构把施加在聚合物上的横向应力巧妙地转化为施加在光栅上的轴向应变,可大大提高其应变传感灵敏度。实验结果表明该传感器不但可以实现压力和温度的同时测量,而且其压力灵敏度系数可达9.65×10-3MPa-1,约为裸光栅的4770倍。     

Research on the fiber Bragg grating sensor for the shock stress measurement

A fiber Bragg grating (FBG) sensor with an unbalanced Mach-Zehnder fiber interferometer for the shock stress measurement is proposed and demonstrated. An analysis relationship between the shock stress and the central reflection wavelength shift of the FBG is firstly derived. In this sensor, the optical path difference of the unbalanced Mach-Zehnder fiber interferometer is ~3.1 mm and the length of the FBG is 2 mm. An arctangent function reduction method, which can avoid sine function's insensitive zone where the shock stress measurement has a reduced accuracy, is presented. A shock stress measurement of water driven by one stage gun (up to 1.4 GPa), with good theoretical accuracy (~10%), is launched.     

基于双通道M-Z干涉仪的FBG光开关研究

为降低电光开光的插入损耗并提高性能,提出了一种基于双通道可调谐马赫-曾德(M-Z)干涉仪制作的光纤布拉格光栅(fiber Bragg grating,简称FBG)光开关,通过改变干涉仪中的可调电动光纤延迟线的延迟时间,实现滤波谱周期的可调谐。通过改变干涉仪其中一臂的延迟时间设定,该光开关能够实现对设定波长光波的开关功能。对光纤M-Z干涉滤波原理进行了理论分析,使用C波段宽带放大自发辐射光源对双通道可调M-Z干涉仪的性能进行了测试。结果表明,其可实现大范围及高精度的滤波调节功能。对基于双通道可调谐马赫-曾德干涉仪制作的FBG光开关,通过FBG开关性能检测系统实验,得到该光开关在波长为1 550nm处的输出光谱,光开关的消光比达到25dB。结果表明,该光开关能够实现大范围高精度滤波功能,具有高消光比、结构简单和易于调节等优点。     

Suppression of side lobes in the fiber Bragg grating reflection spectrum

A revision of works on the methods of writing and apodization of fiber Bragg gratings (FBG) is presented. The possibilities of apodizing FBGs recorded by holographic methods with phase masks and Lloyd interferometer using laser radiation with a Gaussian intensity profile are considered. FBG reflection spectra are numerically simulated for different parameters of the writing beam and configurations of the experimental setup. Side-lobe suppression and FBG spectrum smoothing are experimentally demonstrated. It is shown that this effect is due to equalization of the average value of the induced refractive index in the FBGs. FBG applications, in particular, as frequency selectors in fiber lasers (tunable, narrow-band, and multiwavelength) are described.     

马赫-曾德尔干涉集成化的全光纤磁场与温度传感器

为了简化光纤磁场与温度传感器的结构并提高传感器灵敏度,设计并制作了马赫-曾德尔干涉集成化的全光纤磁场与温度传感器。将单根光纤的马赫-曾德尔模间干涉结构和双臂马赫-曾德尔干涉结构结合:将总长度为1.2m的单模光纤部分制备成长度为2.7cm、锥腰直径为30.1μm的锥形微纳光纤,并得到了拉锥时间与锥腰直径的关系。将锥形微纳光纤放置尼龙槽内并包覆磁凝胶构成传感头,实现模间干涉的马赫-曾德尔磁场传感器;将磁场传感器通过两耦合比为50%∶50%的耦合器并联带有可调谐光衰减器的单模光纤形成马赫-曾德尔干涉的温度传感器。从理论上分析了光谱漂移对磁场和温度传感的特性关系,实验测得室温下磁场强度在25~50mT时,磁场传感的灵敏度为0.301 14nm/mT;在磁场强度为0,温度由25℃升高到30℃时,温度传感的灵敏度为0.518 86nm/℃。该传感器可广泛应用于电力系统放电检测、材料加工、安全监控等领域。     

Simultaneous measurement of refractive index and temperature based on a long period fiber grating inscribed in a photonic crystal fiber with an electric-arc discharge

A novel fiber sensor composed by two single mode fibers and long period fiber grating based on a photonic crystal fiber prepared by periodic discharge heating has been experimentally investigated to measure refractive index and temperature. A Mach-Zehnder interferometer was formed due to the presence of two fusion spliced collapsed regions in the photonic crystal fiber. The resonance dip and interference pattern were differently influenced by the ambient disturbance, so the dual-parameters were simultaneously measured by analyzing the characteristics of transmission spectrum. After the experimental measurements, refractive index and temperature sensitivities of 117.28?nm/RIU and ?86.29?pm/°C were realized. Therefore, the reported sensor with advantages of easy fabrication, simple structure, and small size has the potential for simultaneous refractive index and temperature measurements involving biochemical sensing applications.     

Techniques for DFB Fiber Laser Based Accelerometer

A distributed feedback fiber laser based Bragg grating vibration sensor system is proposed.Demodulated by using an unbalanced M-Z interferometer,experiment demonstrates that the system runs at a sensing sensitivity of about 257.2 rad·s2/m and a resolution of 4.2×10-5 m/s2 for monitoring acceleration.Experimental results show that the phase-shift changes with the acceleration linearly.     

非平衡光纤干涉仪臂差精确测量方法研究

为实现对光纤干涉仪臂差的精确测量,提出了一种采用基于F-P调谐滤波技术的光纤光栅解调系统来精确测量光纤干涉仪臂长差的方法.简要介绍了F-P调谐滤渡法的渡长解调原理,通过分析非平衡迈克尔逊干涉仪的工作原理,指出了输出干涉谱与臂差之间的关系,进而分析了光纤光栅解调仪对干涉仪臂差进行精确测量原理.实验表明该方法可以实现对干涉...     

SIMULTANEOUS MEASUREMENT OF STRAIN AND TEMPERATURE WITH POLARIZATION MAINTAINING FIBER BRAGG GRATING LOOP MIRROR

□ A novel simultaneous method of strain and temperature measurement based on a polarization maintaining fiber Bragg grating loop mirror is proposed and demonstrated. The sensing head was composed of a fiber loop mirror and a section of fiber Bragg grating made of a polarization maintaining fiber. The Bragg wavelengths of the fiber grating in the polarization maintaining fiber were along slow and fast axis showing different sensitivities to strain and temperature with the interferometric peak wavelength of the fiber loop mirror. By monitoring the shifts of the Bragg wavelength and interferometric peak of the fiber loop mirror, with its temperature sensitivity of 0.1167 nm/°C and strain sensitivity of 0.0093 nm/μ?, a temperature measurement resolution about 0.009°C and a strain measurement resolution of 1.08 μ? was achieved theoretically and experimentally.     

波登管式光纤布拉格光栅压强传感器

基于光纤布拉格光栅传感模型，提出了一种悬臂梁与波登管相结合的光纤光栅压强传感器的组合设计，推导了光纤布拉格光栅中心波长偏移量与压强之间的解析关系式。理论和实验结果表明，压强调谐光纤布拉格波长的灵敏度系数的理论值与实验值分别为0．2246nm／MPa、0．2218nm／MPa，在0～6MPa测压范围内，调谐范围为1．35n／n．     

基于光纤布拉格光栅的化学传感器

除掉光纤布拉格光栅的包层,可以使它的布拉格波长对外界环境的折射率变化敏感。采用氢氟酸腐蚀掉光纤布拉格光栅的包层,获得了直径约为6 μm的布拉格光栅。实验研究了布拉格波长对化学溶液的浓度敏感性特征,结果表明:采用10 pm分辨率的光谱仪,丙二醇溶液在低浓度时的浓度分辨率为0.7%,在高浓度时的分辨率为0.32%;糖溶液在低浓度时的分辨率为0.55%,高浓度时为0.1%。采用商用的分辨率为1 pm的高精度波长解调系统,它们的分辨率可以提高一个数量级。     

光纤Bragg光栅靶式流量传感器设计

基于工业流体流量测量技术、光纤布拉格光栅(fiber Bragg grating,FBG)传感检测技术与靶式流量计原理,针对单个光纤Bragg光栅传感系统对温度交叉敏感的问题,设计并且制作了一种基于双光纤Bragg光栅流量传感器。该传感器采用靶盘结构作为光纤Bragg光栅流量传感器的受力元件,对温度起到了补偿作用,并且有效地提高了应变测量灵敏度。实验表明,该流量传感器的线性误差为0.31%。     

Simultaneous measurement of refractive index and temperature by integrating an external Fabry-Perot cavity with a fiber Bragg grating

A fiber sensor for simultaneous measurements of refractive index and temperature based on the integration of a fiber Bragg grating (FBG) with an external Fabry-Perot (F-P) cavity is presented. The fringe contrast of the interference spectrum generated by the F-P cavity is used to determine the external refractive index, while the wavelength shift of the FBG is used to measure temperature. The result showed that the refractive index and temperature sensitivity for the integrated sensor is 8.1 × 10(-6) and 0.01006 nm/°C, respectively.     

一种倾角及温度同时测量的光纤传感器

叙述了一种用于倾斜角及温度同时测量的传感器。该传感器由光纤锥和光纤布拉格光栅构成,当传感器倾角发生改变时引起光纤锥的通光损耗改变,通过测量通光损耗的变化而测量倾角,通过测量光纤光栅的反射波长的变化而实现温度测量,此外光纤布拉格光栅还有提高倾角测量灵敏度的作用。     

啁啾效应对Bragg波长匹配解调精度的影响与消除

介绍了光纤光栅Bragg波长的匹配解调原理,分析了传感光纤光栅和匹配光纤光栅的反射谱相关函数, 说明相关函数与光电探测器输出信号具有线性关系。指出基于最大相关原理(光电探测器输出信号极值判断法)的匹配解调只适用于两个光纤光栅具有相同的反射谱型。采用光电探测器输出信号峰值判读时,传感光纤光栅的啁啾效应会引起Bragg波长的解调误差。理论分析和实验研究表明,对光 电探测器输出信号进行去卷积运算处理可以消除传感光纤光栅啁啾效应对Bragg波长解调精度的影响。     

Determination of refractive index by a U-shaped multimode fiber sensor

The U-shaped multimode fiber structure is proposed to measure the refractive index of liquid. In the previous work, the U-shaped structure by single-mode fiber has been widely investigated. However, the large bending loss restricted its practical applications, especially for the reflection-type fiber probe. To reduce the bending losses, the multimode fiber is used as the bending section of the fiber sensor in this study. The structures with different bending radiuses are fabricated to verify this design. Moreover, to simplify the interrogation method, the differential intensity interrogation method is used by cascading two fiber Bragg gratings after the U-shaped fiber structure. The low bending loss of the proposed structure is helpful to measure the reflected light power by fiber Bragg gratings. The influence of incident light power fluctuation was largely suppressed by this differential method. In addition, the sensitivity is also increased by a factor of 2 compared with the intensity interrogation method using one-cascaded fiber Bragg grating. The experimental results show that the refractive index sensitivities are ?115.09?dB/RIU in the refractive index range of 1.3405–1.3874 and ?260.24?dB/RIU in the refractive index range of 1.3874–1.4223, respectively.     

楔块调整式Talbot干涉仪的光学设计

为改变光纤光栅的写入Bragg波长,研制了包括一块相位模板和两块紫外反射平面镜的楔块调整式Talbot干涉仪。在写入光纤Bragg光栅的过程中,通过调整两平面镜的反射角度可改变由±1级衍射光束经两平面镜反射后形成的干涉条纹的周期。最后,放置在可调谐干涉区的光纤就可刻写成具有不同写入Bragg波长的光纤光栅。值得注意的是通过选择不同倾斜角α的楔形块,决定了光纤光栅的写入Bragg波长的改变率和干涉条纹棱脊位置的位移率。