一种多模-细芯-多模结构的干涉型光纤传感器

设计并制作了一种基于马赫-曾德干涉仪(Mach -Zehnder interferometer,MZI)原理的温度与压力同 时测量的光纤传感器,该传感器采用多模-细芯-多模(Multimode fiber -Thin core fib er- Multimode fiber,MTM)结构,其原理是,当多模光纤(Multimode fiber,MMF)中的光到达第 1个熔接点时 一部分进入细芯光纤(Thin core fiber,TCF)的纤芯,激发起纤芯模;另一部分进入TCF的 包层,激发起 包层模。当这两部分光到达第2个熔接点处时,TCF纤芯中的光进入MMF的纤芯,TCF包层中 的光一部分进入 到MMF的包层,另一部分进入MMF的纤芯,与纤芯模式发生干涉。外界环境如温度、压力等发 生改变时干涉 谱将随之漂移,因此可以通过观察光谱中干涉谷的漂移来测量外界温度、压力的变化。当温 度变化范围为 30℃时,实验测得Dip1、Dip2的温度 灵敏度分别为0.042nm/℃、0.051nm/℃。当 压力变化范围为 0N－9.8N时,实验测得Dip1、Dip2的压力灵敏度分别为－0.240nm/N、－0.524nm/N。由于 Dip1和Dip2对温度 和压力的灵敏度分别不同,因此可以利用矩阵实现对温度和压力的同时测量。该传感器制造 简单精巧,成本较低,具有一定的研究以及应用价值。     

基于磁流体和无芯光纤的磁场传感器

用无芯光纤(NCF)作为单模-多模-单模(SMS)结构中的多模光波导,并将其浸没在密封于毛细管内的磁流体(MF)中,形成了一种新型的全光纤化磁场传感器。传感器可利用磁场变化时其透射谱中谷值波长的移动或峰值波长处的透射率变化对相应的磁场变化进行测量。完成了传感器的制作并进行了实验研究,在传感器长约9cm时,实验得到的磁场灵敏度分别达到了78pm/Oe和0.129dB/Oe。除了作为磁场传感器,本文装置还可以用来作为磁控可调光衰减器或光调制器。     

Optical fiber magnetic field sensors with peanut-shape structure cascaded with LPFG

An optical fiber magnetic field sensor for the dual-parameter simultaneous measurement is proposed and demonstrated. The sensor head is constructed by a peanut-shape structure and long period fiber grating (LPFG) coated by magnetic fluid (MF). The external magnetic field intensity can be measured by the variation of characteristic wavelength (Dip1 and Dip2) in interference spectrum since the effective refractive index of MF changes with external magnetic field intensity. When the external magnetic field intensity changes from 0 mT to 20 mT, the magnetic field sensitivities of Dip1 and Dip2 are ?0.064 nm/mT and ?0.041 nm/mT, respectively. Experimental results show that the temperature sensitivities of the Dip1 and Dip2 are 0.233 nm/°C and 0.186 nm/°C, respectively. Therefore, the simultaneous measurement of the magnetic field intensity and temperature is demonstrated based on the sensitive matrix. It has some potential applications in aerospace, environmental monitoring and medical sensing fields.     

Micro-displacement sensor based on an asymmetric wavy multimode fiber interferometer

We proposed a compact and tunable multimode interferometer(MMI) based on an asymmetric wavy fiber(AMWF), which has axial offset, off-center taper waist, and micro-length. The fabrication process only contains non-axis pulling processes of single-mode fiber on two close positions. Theoretical qualitative analyses and experiments verify the tunable multimode propagation of the AMWF. Experimental results show a nonlinear wavelength response with increasing axis displacement from 0 to 120 μm. In the...     

基于单模-多模-单模光纤模间干涉的传感系统

基于单模-多模-单模光纤（SMS）结构的模间干涉现象,在外界环境变化时SMS 光纤结构输出光场散斑图样的变化规律,提出了一种用于振动、应力及温度检测的光纤传感系统。该系统使用光电二极管测量散斑图样部分固定区域的光功率变化,即可得到施加在多模光纤上的外界应力,通过FFT 和Hilbert 变换,可得到外界振动（频率、幅度）和温度变化信息。对该系统的振动测量和温度测量进行定标后,经实验研究测得,该系统振动测量误差小于0.7 Hz,温度测量误差小于5.0%。该系统结构简单,成本低,并可用于多参量的测量。     

An optical fiber magnetic field sensor based on fiber spherical structure interferometer coated by magnetic fluid

A novel magnetic field sensor based on optical fiber Mach-Zehnder interferometer (MZI) coated by magnetic fluid (MF) is proposed. The MZI consists of two spherical structures formed on standard single mode fiber (SMF). The interference wavelength and the power of the sensing structure are sensitive to the external refractive index (RI). Since RI of the MF is sensitive to the magnetic field, the magnetic field measurement can be realized by detecting the variation of the interference spectrum. Experimental results show that the wavelength and the power of interference dip both increase with the increase of magnetic field intensity.     

基于腐蚀型多模光纤的干涉型传感器实现温度和液位同时测量

提出了一种新颖的基于腐蚀型多模光纤(MMF)级联 的干涉型光纤传感器。在芯径为50μm的MMF1左侧熔接一段被腐蚀的芯径为105μm的大芯径MMF2构成传感区域。 实验中,MMF2的包 层采用HF溶液腐蚀的方法去除。由于纤芯失配,两段MMF内部均产生多种纤 芯模式,它们 之间相互干涉,随之产生一系列具有不同灵敏特性的干涉峰。利用干涉谱中不同波谷对温度 和液位的灵敏 度差异,实现对温度和液位的同时测量。测得3个波谷的温度灵敏度分别为0.066nm/℃、0.139nm/℃和 0.031nm/℃;通过对水和盐水的液位进行实验对比发现,传感器对盐水的液 位灵敏度较高,测得液位灵敏 度最高可达－1.251nm/mm。实验表明,本文传感系统成本低、结构 简单,可用于温度和液位的同时测量,在石油开采、生物制药等方面具有潜在的应用价值。     

基于空心光纤多模干涉的折射率传感器研究

基于空心光纤(HF)多模干涉原理提出一种新颖光纤折射率传感器,实现了对环境溶液折射率的测量。这种光纤折射率传感器不仅制作简单、成本低廉,而且为波长编码、抗干扰性好。实验表明,这种光纤折射率传感器其有效传感范围为1.333～1.450,并且当溶液折射率小于1.40时,特征波长与折射率近似呈线性关系,灵敏度为88.07 nm。针对相同折射率不同溶质的溶液,传感器出射光谱能量差异表明,该结构的光纤传感器在物质检测方面有着潜在的应用。     

Research on SFTS structure based optical fiber sensor

A single-mode-few-mode-thin-core-single-mode (SFTS) structure based optical fiber sensor is fabricated and experimentally studied. The sensing principle relies on the inter-modal interference. Since the core diameter of few-mode fiber (FMF) is larger than that of single-mode fiber (SMF), the FMF helps to allow more light to enter the cladding of thin-core fiber (TCF), which helps TCF to excite cladding modes. The interference between core and cladding modes in TCF occurs at the joint of lead-out SMF and TCF. Experimental results demonstrate a refractive index (RI) sensitivity of ?103.34 nm/RIU and a temperature sensitivity of 0.05 nm/°C. The proposed sensor not only can measure temperature, but also can measure RI. In addition, the proposed sensor is simple for without complicated fabrication process.     

Microbend sensor structure for use in distributed andquasi-distributed sensor systems based on selective launching andfiltering of the modes in graded index multimode fiber

This paper describes a novel optical fiber microbend sensor architecture which my be utilized in distributed and quasi-distributed measurement. The actual sensor element is graded index multimode fiber coupled to the measurand field through the usual microbend inducing structures. However, the feed to the sensing section is through a single-mode fiber spliced to the multimode fiber to ensure that only the lowest order spatial mode is launched. Similarly the receiver is also coupled to the sensing element through a single mode fiber. The single mode within multimode fiber propagates with minimal mode coupling with source to receiver losses of typically 0.7 dB for short sensors ranging to approximately 0.3 dB per each additional kilometer of sensing fiber. The sensitivity of this structure to microbend induced losses has been thoroughly characterized. Typically the optical power loss for a given microbend structure and force is about three to six times higher in this architecture than for conventional fully mode filled microbend sensor. The structure is also almost totally insensitive to macrobend induced losses and allows a variety of novel designs in microbend inducing structures. Additionally, spatial mode filters allow effective control over concatenation effects that are common in microbend sensors     

基于光纤锥和多模渐变光纤的马赫-曾德尔干涉仪的传感特性研究

提出了一种基于光纤锥和纤芯失配光纤结构的马赫-曾德尔干涉(MZI)传感器。在距离单模光纤(SMF)锥25mm处熔接一段长30mm的多模渐变光纤(GI MMF),形成SMF-光纤锥-SMFGI MMF-SMF结构。其中,光纤锥起到增加包层模能量的作用,GI MMF为传感臂。传感器外界环境温度、折射率及应力的改变都会使传感器的纤芯基模和包层模的光程差发生改变,从而引起传感器干涉谱发生变化,通过监测干涉谱的变化可以实现对外界物理量的测量。实验研究结果表明,当环境溶液温度在30~89℃范围内变化时,传感器的温度灵敏度为78.6pm/℃,线性度为0.997;环境溶液折射率在1.333~1.394变化范围内,传感器的折射率灵敏度为81.48dB/RIU,线性度为0.989;轴向应变在0~933.3με变化范围内,传感器的应变灵敏度为0.33×10-2 dB/με,线性度为0.998。本文传感器可以实现多个物理量的同时区分测量。     

基于硅桥结构的MEMS磁场传感器

提出了一种基于硅桥结构的MEMS磁场传感器结构。其结构由制作在硅桥敏感膜表面的惠斯通电桥和在膜中间沾上铁磁体制成。当传感器处于磁场中时,铁磁体在外磁场中磁化产生磁力,磁力会使硅敏感膜弯曲从而引起压阻改变进而使惠斯通电桥产生电压输出以达到测量磁场的目的。文章通过有限元软件仿真对铁磁体的尺寸进行了优化。实验结果和理论结果较接近。实验测得该传感器最大灵敏度为48mV/T,分辨率为160μT,该传感器可以用来进行强磁场的测量。实验结果结果表明:传感器的重复性和动态响应时间分别约为0.66%和150ms。     

MEMS magnetic field sensor based on silicon bridge structure

A MEMS piezoresistive magnetic field sensor based on a silicon bridge structure has been simulated and tested.The sensor consists of a silicon sensitivity diaphragm embedded with a piezoresistive Wheatstone bridge,and a ferromagnetic magnet adhered to the sensitivity diaphragm.When the sensor is subjected to an external magnetic field, the magnetic force bends the silicon sensitivity diaphragm,producing stress and resistors change of the Wheatstone bridge and the output voltage of the sensor.Good agreeme...     

A biological fluid fiber Sagnac sensor based on SPF-PCF-SPF structure

A biological solution concentration sensor based on a side-polished fiber (SPF) assisted fluid system is presented. The birefringence properties of the asymmetrically filled fluid in this structure and the relationship between the concentration of the biological solution and the refractive index are theoretically analyzed. It was found that the interference peaks had red-shifted with increasing concentration. A sensing sensitivity of 1.387 1×104 nm·mL/mol at 14.68×10-4 mol/mL was achieved within the experimental range after different concentrations of arginine solutions were injected into the sensing system. This sensing system can also be applied to measure the concentration of other biological solutions, providing the feasibility of real-time detection of biological solutions.     

Wavelength tunable fiber lens based on multimode interference

A new concept for a fiber-based wavelength-tunable condensing lens is theoretically and experimentally investigated in terms of its ability to shift the longitudinal focus position as a function of wavelength. By exploiting multimode interference effects with reimaging theory, a compact and robust device, completely contained within a standard FC connector, can be constructed by simply splicing a single-mode fiber (SMF) to a finite length section of multimode fiber (MMF). This paper summarizes the theoretical and experimental results of such a device, with additional results for wavelength sensitivity.     

基于掺铒光纤环形滤波器和多模光纤光栅的双波长激光器

提出了基于掺铒光纤环形滤波器和多模光纤光栅的双波长激光器。在单波长光纤激光器的基础上,增加了多模光纤布拉格光栅(MM-FBG)和高精细度的光纤滤波器。其中多模光纤布拉格光栅作为激光器的波长选择元件,可产生两个波长的激光输出。高精细度的光纤滤波器由两个光耦合器和一段弱泵浦的掺铒光纤构成,掺铒光纤产生的增益和光纤时延使滤波器具有高精细度的梳状谱响应,从而抑制了激光器产生的不需要模式,保证了输出的激光具有窄线宽特性。以980 nm的激光二极管(LD)作为泵源,得到了线宽为0.07 nm或0.08 nm的双波长输出,表明滤波器具有良好的滤波效果。     

基于光纤传感器的油井温度场监测研究

针对目前油井井温常规测量方法存在的不足,提出了一种基于喇曼散射原理的油井温度在线监测方案,对其可行性进行了分析验证,构建了基于分布式光纤传感器的油井温度场监测系统.实验证明该系统具有良好的空间定位精度和温度分辨率,可以在不影响温度场原始分布的情况下实现对多点温度的分布式实时快速测量.     

Research on optical fiber magnetic field sensors based on multi-mode fiber and spherical structure

A magnetic field sensor with a magnetic fluid (MF)-coated intermodal interferometer is proposed and experimentally demonstrated. The interferometer is formed by sandwiching a segment of single mode fiber (SMF) between a segment of multi-mode fiber (MMF) and a spherical structure. It can be considered as a cascade of the traditional SMF-MMF-SMF structure and MMF-SMF-sphere structure. The transmission spectral characteristics change with the variation of applied magnetic field. The experimental results exhibit that the magnetic field sensitivities for wavelength and transmission loss are 0.047 nm/mT and 0.215 dB/mT for the interference dip around 1 535.36 nm. For the interference dip around 1548.41nm, the sensitivities are 0.077 nm/mT and 0.243 dB/mT. Simultaneous measurement can be realized according to the different spectral responses.     

Evanescent field absorption sensor for detection of copper （Ⅱ） in water using multimode optical fiber

The evanescent field absorption sensor for the detection of trace amount of copper （Ⅱ） in water is experimentally analyzed with the etched step index multimode plastic clad silica （PCS） fiber. The designed sensor is sensitive to copper （Ⅱ） content in water with a range up to 250 ppm.