基于掺铒光纤的微型光纤法布里-珀罗干涉传感器

提出了一种化学腐蚀掺铒光纤制作微型光纤法布里-珀罗干涉传感器的方法。通过对掺铒光纤进行化学腐蚀,形成凹槽,再与单模光纤直接熔接制作而成。实验制作的微型法布里-珀罗干涉传感器干涉条纹光滑,对比度达到15dB。对该微型光纤法布里珀罗干涉腔进行了应变和温度传感实验。实验结果表明,在0-600με￡内,波谷移动随应变改变的灵敏度达到1．7pm／με,线性度为0．9998,从73～23℃,波谷移动随温度改变的灵敏度3．9pm／℃,线性度为0．9982。该方法制作的微型光纤法布里-珀罗传感器具有操作简单,一次成型,制作成本低的优点。     

Fiber-optic Fabry-Prot strain sensor based on graded-index multimode fiber

By using a graded-index multimode fiber (GI-MMF) with a relatively flat index profile and high refractive index of the fiber core, a microextrinsic fiber-optic Fabry Prot interferometric (MEFPI) strain sensor is fabricated through chemical etching and fusion splicing. Higher reflectance of the microcavity is obtained due to the less-curved inner wall in the center of the fiber core after etching and higher index contrast between the GI-MMF core and air. The maximum reflection of the sensor is enhanced 12 dB than that obtained by etching of the Er- or B-doped fibers. High fringe contrast of 22 dB is obtained. The strain and temperature responses of the MEFPI sensors are investigated in this experiment. Good linearity and high sensitivity are achieved, with wavelength-strain and wavelength-temperature sensitivities of 7.82 pm/με and 5.01 pm/°C, respectively.     

Optical fiber strain sensor using fiber resonator based on frequency comb Vernier spectroscopy

A novel (to our best knowledge) optical fiber strain sensor using a fiber ring resonator based on frequency comb Vernier spectroscopy is proposed and demonstrated. A passively mode-locked optical fiber laser is employed to generate a phased-locked frequency comb. Strain applied to the optical fiber of the fiber ring resonator can be measured with the transmission spectrum. A good linearity is obtained between displacement and the inverse of wavelength spacing with an R(2) of 0.9989, and high sensitivities better than 40 pm/με within the range of 0 to 10 με are achieved. The sensitivity can be proportionally improved by increasing the length of the optical fiber ring resonator.     

高灵敏度光纤应变传感器

提出一种基于锥形光纤和光纤F-P腔组合结构的光纤应变传感器。该传感器包含单模光纤拉锥形成的锥区和石英毛细管构建的F-P腔2个应变敏感区域。理论分析了光波在该传感器中的传播过程,获得了该传感器的光强传输函数。由于锥形光纤中激发出的包层高阶模参与干涉,导致传感器干涉光谱具有调制特性。实验获得了该传感器的干涉光谱,通过分析谐振波长偏移或消光比变化对应变实现独立测量,在0~500 με的测量范围内,该传感器的应变灵敏度为14.6 pm/με。利用锥形光纤引发的模式干涉和F-P腔的双光束干涉效应共同作用形成受调制的干涉谱型进行应变传感,应变灵敏度高,同时具备2种独立的应变检测手段(谐振波长和消光比检测)。     

Axial strain and temperature sensing characteristics of the single–coreless–single mode fiber structure-based fiber ring laser

This paper experimentally demonstrated a singlemode–coreless–singlemode (SCS) fiber structure-based fiber ring cavity laser for strain and temperature measurement. The basis of the sensing system is the multimodal interference occurs in coreless fiber, and the transmission spectrum is sensitive to the ambient perturbation. In this sensing system, the SCS fiber structure not only acts as the sensing head of the sensor but also the band-pass filter of the ring laser. Blue shift with strain sensitivity of \(\sim\) ?2 pm/με ranging from 0 to 730 με and red shift with temperature sensitivity of \(\sim\) 11 pm/°C ranging from 5 to 75 °C have been achieved. Experimental results also show the proposal has great potential in using long-distance operation. The fiber ring laser sensing system has a optical signal to noise ratio (OSNR) more than 50 and 3 dB bandwidth less than 0.05 nm. The result shows that the coreless fiber has no improvement of the temperature and axial strain sensitivity. However, compared to the common singlemode–multimode–singlemode fiber structure sensors, the laser sensing system has the additional advantages of high OSNR, high intensity and narrow 3 dB bandwidth, and thus improves the accuracy.     

Optical fiber strain and temperature sensor based on an in-line Mach–Zehnder interferometer using thin-core fiber

We propose and demonstrate a fiber in-line Mach–Zehnder interferometer using thin-core fibers. This in-line interferometer is composed of a short section of thin-core fiber inserted between two single mode fibers (SMF), and demonstrated as a strain and temperature sensor in this study. A strain sensitivity of ?1.83 pm/με with a measurement range of 0?2000 με, and the temperature sensitivity of ?72.89 pm/°C with a temperature variation of 50 °C are achieved. We also discussed that the influence of strain and temperature change on the relative power ratios among the excited cladding modes in thin-core fibers.     

All-solid multi-core fiber-based multipath Mach–Zehnder interferometer for temperature sensing

A novel multipath Mach–Zehnder interferometer (m-MZI) is proposed and experimentally demonstrated, which is fabricated by fusion splicing a segment of all-solid multi-core fiber (MCF) between two sections of single mode fiber-28 with a well-controlled lateral offset at the splice points. Beam propagation method-based simulation results demonstrated light passing throw MCF from multiple paths. Experiments with different lengths of MCF were implemented to investigate our proposed m-MZI’s response to temperature and strain. Compared with previously reported optical fiber modal interferometers, higher phase sensitivity can be obtained in our scheme due to the multipath interference configuration embedded in one fiber. A very high temperature sensitivity of 130.6 pm/°C has been achieved, and the maximum strain sensitivity is less than 0.284 pm/με in all experiments. A record low strain-to-temperature cross-sensitivity of 6.2 × 10^?4 °C/με has been realized, and it shows great significance of this in-fiber integrated multipath Mach–Zehnder interferometer in practical temperature sensing applications.     

All-Fiber Dual-Parameter Sensor Based on Cascaded Long Period Fiber Grating Pair Fabricated by Femtosecond Laser and CO2 Laser

An all-fiber dual-parameter sensor based on cascaded long period grating pair fabricated by femtosecond laser and CO₂ laser has been proposed and realized both theoretically and experimentally. The resonant wavelengths of LPFGs are 1557.80 nm and 1590.88 nm. In the strain range of 0–400 με, strain sensitivities are ?7.2 pm/με for C-LPFG and ?1.6 pm/με for F-LPFG. In the temperature range of 30–70°C, temperature sensitivities are ?41.1 pm/°C for C-LPFG and ?21.2 pm/°C for F-LPFG. By analyzing the resonant wavelength characterization, the proposed sensor can be efficiently used for dual-parameters measurement with promising application prospect and great research reference value.     

Highly sensitive long-period fiber-grating strain sensor with low temperature sensitivity

A long-period fiber-grating sensor with a high strain sensitivity of -7.6 pm/microepsilon and a low temperature sensitivity of 3.91 pm/ degrees C is fabricated by use of focused CO(2) laser beam to carve periodic grooves on a large- mode-area photonic crystal fiber. Such a strain sensor can effectively reduce the cross-sensitivity between strain and temperature, and the temperature-induced strain error obtained is only 0.5 microepsilon/ degrees C without using temperature compensation.     

合金钢封装光纤Bragg光栅传感器传感特性的研究

提出了一种光纤光栅新型合金钢封装结构。利用等强度悬臂梁和温度控制箱对合金钢封装光纤布拉格光栅的应力和温度传感特性进行了测量。实验表明,采用该种封装的光纤光栅传感器保持了裸光纤光栅的响应灵敏度,其拉应变灵敏度系数为1.17pm/με,压应变灵敏度系数为1.2pm/με,温度灵敏度系数为11.3pm/℃,线性响应度在0.9995以上,可满足实际应用的要求。     

具有实时监测能力的光纤光栅传感系统时域地址查询技术

时钟信号控制下的脉冲宽带光源发出的光波,进入4个光栅组成的间距为10m的光栅串。利用受同一时钟信号控制的1×4模拟电子开关,将各传感元的反射光脉冲依次分配至相应的输出信道,实现时域地址查询,并对各传感元位置的待测应变进行实时监测。引入非平衡迈克耳孙干涉解调装置,将来自传感光栅的受待测应变诱导而至的波长漂移信息变为相移信息,定标后便可实现传感信号的解调。1556nm波长时,系统传感灵敏度的实验值为1.658°/με,与理论值1.673°/με基本吻合。     

基于纤芯失配和光纤布拉格光栅实现温度和应变同时测量

基于纤芯失配理论,提出了一种多模单模多模（MSM）结构与光纤布拉格光栅（FBG）级联实现温度和应变同时测量的光纤传感器。利用MSM结构的干涉谱和FBG对温度和应变的不同响应灵敏度,实现了对温度、应变的同时测量。实验结果表明,在20 ℃~80 ℃的温度范围内,MSM结构的干涉谱和FBG的温度灵敏度分别为0.091 nm/℃和0.0102 nm/℃;在0～650 με的应变范围内,应变灵敏度分别为 -0.0013 nm/με和0.0012 nm/με。因此利用敏感矩阵,即可实现对温度和应变的同时测量,且温度和应变的最大测量误差分别为±0.2 ℃和±8.25 με。该结构灵敏度高,结构简单,且不易受电磁等干扰,实验结果具有良好的线性度,在工程领域应用前景良好。     

Integration of miniature Fabry-Perot fiber optic sensor with FBG for the measurement of temperature and strain

A sensor has been fabricated by the integration of a fiber Bragg gating sensor (FBGs) with a fiber Fabry-Perot (F-P) sensor fabricated by etching method. In the integrated sensor, the FBG was used to measure temperature, while the fiber Fabry-Perot interferometer sensor (FFPIs) was used for strain measurement. Wavelength decoding for FBG and peak tracking for FFPI was employed for demodulation, respectively. The result showed that the temperature and strain sensitivity for the integrated sensor is ~ 2.7 pm/μεand ~ 9.3 pm/°C, respectively.     

具有温度自校准功能的光纤折射率传感器

提出一种具有温度自校准功能的光纤折射率（RI）传感器,传感头结构由2段很短的多模光纤（MMF）之间夹熔一段对折射率不敏感的光纤布拉格光栅（FBG）构成,传感头总长度为14 mm,FBG可以为折射率测量提供良好的温度校准功能。实验结果证明,该传感器的折射率灵敏度为126 nm。其干涉光谱共振波长的温度灵敏度为35.09 pm/℃,用于温度校准的FBG的温度灵敏度为11.14 pm/℃。相比于普通的折射率传感器,这种具有温度自校准功能的折射率传感器具有良好的实用前景。     

基于FBG的液压系统中流量/压力/温度同时测量技术

针对传统液压系统检测中存在的传感器功能单一、体积较大、测量精度不高等问题,提出一种光纤光栅复合传感器.该传感器以一体化的靶片式流量传感结构为基础,融合光纤光栅压力和温度传感器,可以实现对液压系统流量、压力和温度的同时测量.在对各参数传感模型理论分析的基础上,对传感器的结构进行设计,并制作了传感器实物.利用液压综合试验系统等设备对传感器进行了性能测试和参数标定,得到其流量灵敏度为0.049L/s,压力灵敏度为28.4pm/Mpa,温度灵敏度为14.9pm/℃,验证了传感器设计的合理性.同时,传感器的温度测量功能可在流量和压力测量中作为参考,克服温度的交叉敏感效应,提高传感器的环境适应能力.     

基于拉锥光纤布拉格光栅的法布里-珀罗应变传感器的仿真研究

为解决干涉型光纤应变传感器自由光谱范围较小或干涉条纹精细度较低等问题,提出了一种基于单拉锥光纤布拉格光栅的法布里-珀罗腔的应变传感结构及其改进方案。利用啁啾光纤布拉格光栅不同位置反射不同波长的特性,形成腔长随波长连续变化的法布里-珀罗腔,得到了无穷大的自由光谱范围且谐振谷精细度高。数值计算结果表明,应变传感灵敏度与拉锥光纤的腰区直径和栅区长度正相关。在0～300 με范围内,当腰区直径为光纤直径的3/25,栅区长度为30 mm时,应变传感灵敏度为7.05 pm/με。该结果对其他干涉型传感结构的设计具有一定的参考价值。     

Single S-tapered fiber Mach-Zehnder interferometers

A fiber Mach-Zehnder interferometer (MZI) sensor, novel to our knowledge, based on a single "S"-like fiber taper has been fabricated via applying nonaxial pull in fiber tapering by a fusion splicer. The typical feature size of the structure has a length of 660 μm and the axial offset of 96 μm. This S fiber taper MZI has a refractive index (RI) sensitivity of 1590 nm/refractive index unit in the RI range of 1.409-1.425 and a strain sensitivity of about -60 pm/microstrain, which is 30 times higher than that of the normal two-taper-based MZI sensors.     

可同时测量蔗糖浓度和温度的组合光纤光栅传感器

为了实现蔗糖溶液浓度与温度的同步精确测量,采用组合式光纤光栅,通过线性折射率分区,构成相应的系数矩阵。首先,基于模式耦合理论,采用光纤布拉格光栅（FBG）和长周期光纤光栅（LPBG）形成组合式光纤光栅,实现了双参数测量的光学传感器。此组合式光纤光栅结构中,FBG响应温度测量,LPFG同时响应蔗糖溶液浓度和温度测量。然后,在两个线性折射率范围,即1.33~1.42和1.42~1.44中,校正温度和蔗糖溶液浓度的相关系数。最后,构成两个敏感系数矩阵,来讨论蔗糖溶液浓度和温度同时测量的方法。实验结果表明：蔗糖溶液浓度测量灵敏度达到-213.5 pm/RIU,温度测量灵敏度达到117.9 pm/K。因此,组合式光纤光栅传感器作为光化学传感器具有高灵敏度的特性。     

基于游标效应的增敏型光纤法布里-珀罗干涉仪温度传感器

本文介绍了一种高灵敏度光纤温度传感器.该传感器由一小段毛细管熔接于单模光纤和一段大模场光纤之间而构成串联的两个法布里-珀罗干涉仪.由于俩干涉仪具有相近的自由光谱区,因而它们的叠加光谱会产生游标效应.实验结果显示,利用游标效应解调,该传感器的温度灵敏度可从单一空气腔法布里-珀罗干涉仪的0.71 pm/℃提高到179.30 pm/℃.该传感器结构紧凑(1 mm)且灵敏度高,具有良好的应用前景.