Refractive index sensors based on the fused tapered special multi-mode fiber

In this paper, a novel refractive index (RI) sensor is proposed based on the fused tapered special multi-mode fiber (SMMF). Firstly, a section of SMMF is spliced between two single-mode fibers (SMFs). Then, the SMMF is processed by a fused tapering machine, and a tapered fiber structure is fabricated. Finally, a fused tapered SMMF sensor is obtained for measuring external RI. The RI sensing mechanism of tapered SMMF sensor is analyzed in detail. For different fused tapering lengths, the experimental results show that the RI sensitivity can be up to 444.517 81 nm/RIU in the RI range of 1.334 9—1.347 0. The RI sensitivity is increased with the increase of fused tapering length. Moreover, it has many advantages, including high sensitivity, compact structure, fast response and wide application range. So it can be used to measure the solution concentration in the fields of biochemistry, health care and food processing.     

Highly Sensitive Photonic Crystal Fiber-Based Refractive Index Sensing Using Mechanical Long-Period Grating

We experimentally demonstrate a novel refractive index (RI) sensor with the measurand infiltrated into the air channels of a single mode photonic crystal fiber (PCF). A tunable long-period grating is formed in a short length of PCF by use of the periodic mechanical pressure. Resonance shift with the change of the infiltrated liquid is observed with a sensitivity of ${hbox{4.1}} times {hbox{10}}^{-6}$ RI unit in a refractive index range from 1.32 to 1.39. The thermal stability of the pure-silica-based PCF device shows a three times better performance compared with conventional single mode fiber.      

填充混合液体的光子晶体光纤温度传感研究

为获得高灵敏度光子晶体光纤温度传感,在实心光子晶体光纤（PCF）空气孔中填充氯仿和酒精等高折射率热敏液体的混合物。理论上采用有限元法分析了温度对光纤模场面积和限制损耗的影响。通过调节液体的混合比,使损耗对温度的灵敏度达到最大值,实现了高灵敏度PCF温度传感。实验表明,填充液体的长为4mm的PCF温度传感器,灵敏度经检测...     

A new photonic crystal fiber gas sensor based on evanescent wave in terahertz wave band: design and simulation

In this paper, we present the design of a new photonic crystal fiber （PCF） gas sensor for evanescent-field sensing in terahertz （THz） wave band. This sensor can be used to identify the gas, and its size is very large, so that it is beneficial to fill it with the test substance. Based on simulation, we demonstrate that the gas sensor using PCFs with four noncir- cular large holes in the cladding has high sensitivity and low loss, the confinement loss is less than 0.007 dB/m, and the bending loss is very small. The new PCF gas sensor can detect kinds of gases, for example, if test gas is water va- por, it has obvious absorption peaks in THz band, and the sensitivities of gas sensor are 64% and 73% at 1.097 THz and 0.752 THz, respectively. Due to the ultra-low loss and high sensitivity of the model, the novel steering-wheel structured fiber is very suitable for evanescent-field sensing and the detection of chemical and biological products.     

基于表面等离子体共振的高灵敏度光纤微流控芯片

设计了一种可嵌入基于表面等离子体共振(SPR)光纤传感器的微流控芯片,可用于溶液浓度的测量。采用具有良好化学惰性的有机聚合材料聚二甲基硅氧烷(PDMS)作为芯片主体的制作材料,在芯片中微流控通道内采用镀有60 nm金膜的多模光纤-光子晶体光纤-多模光纤(MMF-PCF-MMF)传感结构来激发SPR效应。当注入微流体通道的溶液浓度发生变化时,由于光纤传感部分外部折射率的变化引起SPR谐振谷移动,故该芯片可用于测量溶液浓度。本芯片微流控通道直径为0.2 mm,最高检测灵敏度可达8240.6 nm/RIU,具有便于实时测量、高灵敏度、高可靠性、溶液用量少等特点。     

Dynamic Pressure Sensing Study Using Photonic Crystal Fiber: Application to Tsunami Sensing

The present work aims at the study of dynamic pressure sensing using photonic crystal fiber (PCF) for tsunami detection. A distinguishing feature of this work is the use of a PCF sensor for tsunami detection. High-pressure sensitivity along with the negligible temperature sensitivity of the sensor makes it work in a harsh environment like the ocean bottom. First, numerical analysis for various dynamic pressure responses has been carried out and then it is followed by simulation specifically for the case of tsunamis. Results demonstrate that temperature variation in the ocean bottom has very little effect on tsunami detection. The study shows that a PCF-based sensor has the potential to be deployed in the existing tsunami detection systems with the added advantage of simple design.     

Current status of micro- and nano-structured optical fiber sensors

Recently developed micro- and nano-structured optical fiber sensors, with particular reference to surface plasmon resonance (SPR) fiber sensors and photonic crystal fiber (PCF) sensors are reviewed. SPR fiber sensors can have diverse structures such as D-shape, cladding-off, fiber tip or tapered fiber structures. Some of the recently developed novel structures include the use of various types of fiber gratings in SPR fiber sensors. PCF sensors cover diverse recent developments on photonic-bandgap fiber, holey fiber, hole-assisted fiber and Bragg fiber sensors. Major applications of these include gas sensors and bio-sensors. These micro- and nano-structured fiber sensors have attracted considerable research and development interest, because of their distinct advantages, which include high sensitivity, small sensor head footprint and the flexibility of the optical fibers. They are also of academic interest, and many novel ideas are continuously developed.     

光子晶体光纤的设计与应用研究综述

光子晶体光纤具有较强的可设计性,一般通过改变光子晶体光纤包层中空气孔的大小、形状或者排列方式对光纤的传输特性进行调节,以此实现高双折射、高非线性、平坦色散及低限制性损耗等特性。光子晶体光纤的传输特性在不同领域中具有较大的应用价值,如分布式传感、飞秒激光器和气体传感器等。文章首先介绍了光子晶体光纤的结构特征以及与普通单模光纤的区别,在此基础上针对各种典型的光子晶体光纤结构分析了其色散和非线性等传输特性。详细介绍了基于光子晶体光纤的分布式光纤传感、飞秒激光器和气体传感器的传感机理以及达到的传感性能,并与非基于光子晶体光纤的传感器的传感性能进行了比较,验证了基于光子晶体光纤传感器的优异性能。最后对光子晶体光纤的发展及应用进行了总结与展望。     

Photonic crystal fiber sensors for minimally invasive surgical devices

The measurement of interaction forces in minimally invasive surgical devices, sensorized with photonic crystal fiber (PCF) sensors, is presented in this paper. Two types of PCF sensors are used: a tapered PCF interferometer and a microhole-collapsed PCF interferometer for the detection of interaction forces generated in surgical devices without the influence of ambient temperature variation. The demonstration devices used for force characterization are a laparoscopic scissor and a standard surgical scissor blade. The force sensitivity of each sensorized blade is examined and compared with fiber Bragg grating (FBG)-sensorized blades. Results show that the PCF-sensorized surgical blades outperform the blades fitted with the FBG sensors during static load measurement.     

基于银纳米颗粒的HCPCFSERS传感系统优化设计

银纳米颗粒与光子晶体光纤、表面增强拉曼散射效应结合而成的PCF SERS传感器得到了科研界的广泛关注.而PCF结构、SERS基底的性能是传感器的重要影响因素.为了进一步提高SERS PCF传感器的性能,通过研究对比PCF和SERS基底结构参数对传感性能的影响,设计出适用于PCF SERS传感的空芯PCF以及SERS基底的结构参数.通过数值计算,设计的空芯PCF空气填充率为56.30%,当激发光波长785 nm时存在光子带隙,并能够实现单模传输.而半径为38 nm的银纳米球在间距为0.7 nm时能够产生最大的SERS增强因子.研究证明,设计的空芯PCF在785 nm输入波长下既能够基模传输激发光,又能够为SERS提供理想的活性面积,而且银纳米颗粒的形状、尺寸、间距对SERS性能影响严重,而且与入射波长有很强的依赖关系.     

Analysis of photonic crystal fiber sensor character

The special character of a PCF which is used as a gas or liquid sensor is discussed. The field distribution is analyzed when the solid core PCF is injected with different medium that has different relative dielectric constant(or refractive index) . And the experiential formulas of the relation between refractive index of some kinds of liquid and their concentration are given,in order to measure the concentration of the relative liquid. At the same time,the effect of propagation constant on PCF sensor character is also discussed. Furthermore,the photonic band-gap(PBG) of PCF(PBG-PCF) is calculated at different medium relative dielectric constant,when it is injected with different medium. That is the principle basis for this kind of PCF sensors.     

干涉型PCF传感器的设计与研究

文章利用长周期光栅的耦合作用,设计了一种级联长周期光栅的PCF(光子晶体光纤)传感器,并对其应变传感特性进行了研究。分析了应变对级联长周期光栅的干涉谱的影响,计算了应变与干涉峰的关系,结果表明,该结构具有较高的灵敏度及较好的线性关系。     

High resolution refractive index sensing with cladded multimode tapered optical fibre

A new fibre-optic refractive index sensor is presented. It is based on the radiation losses introduced by the sample medium in a cladded multimode tapered fibre. A simple light transmission measurement setup is used to test some samples. It is demonstrated that the sensor is suitable for measuring RI in the range 1.36 to 1.46, as well as RI changes below 10/sup -4/.     

Nonadiabatic tapered single-mode fiber coated with humidity sensitive nanofilms

A new humidity sensor has been developed by coating a tapered single-mode standard communications fiber with a humidity sensitive nanofilm using the electrostatic self-assembled (ESA) monolayer technique. Power changes up to 20 dB have been recorded during the coating process. In order to take advantage of both the potential sensitivity of the tapered fiber and the precise thickness control, which is possible to achieve using the ESA technique, the optimal layer thickness has been adjusted to the maximum slope point of the transmitted optical power curve as a function of the overlay thickness. An optimal working point sensor is compared to a nonoptimal one demonstrating the sensitivity difference between both.     

模式识别的光子晶体光纤传感器误差校正研究

为了克服当前光子晶体光纤传感器误差校正方法存在的不足,提出了模式识别的光子晶体光纤传感器误差校正方法。首先分析光子晶体光纤传感器误差产生原因,然后采集光子晶体光纤传感器误差历史数据,引入模式识别技术对光子晶体光纤传感器误差进行学习,并对光子晶体光纤传感器误差进行校正,最后并与其它方法进行了光子晶体光纤传感器误差校正仿真实验。结果表明,本文方法提升了光子晶体光纤传感器误差校正准确性,能够刻画光子晶体光纤传感器误差变化趋势,光子晶体光纤传感器误差校正效果明显好于对比方法,验证了本文方法的优势。     

基于拉锥单模-多模-单模光纤结构的高灵敏折射率传感器

文章介绍基于拉锥单模-多模-单模(SMS)光纤结构的模间干涉仪,当拉伸长度为35mm时形成自由光谱区(FSR)为1.3nm的干涉透射谱,消光比达到10dB。此时拉锥多模光纤的腰椎平坦区直径约为3.85μm,具有较强的倏逝场,可用作高灵敏折射率传感器。实验证明,此拉锥SMS结构在折射率范围1.35-1.36内的灵敏度高达771nm/RIU,能精密监测溶液溶质扩散现象。     

基于强度检测的HiBi-PCF-FLM温度不敏感应力传感器

提出一种基于强度检测的高双折射光子晶体光纤环镜(HiBi-PCF-FLM,highly birefringent photonic crystal fiber loop mirror)温度不敏感应力传感器。利用PCF对温度的不敏感性,把一小段HiBi-PCF传感光纤插入到FLM中,可实现温度不敏感应力传感。利用应力作用引起FLM透射光谱移动的特性,由DFB激光作为入射光源,使用光功率计检测经过FLM后的透射光强度,实现基于强度检测的应力传感。当输入波长为1547 nm时,作用于PCF应力与经过FLM后透射光强度的关系可拟合为二次函数,其与实验数据的拟合度高达0.9995。     

A surface plasmon resonance sensor based on a multi-core photonic crystal fiber

A surface plasmon resonance(SPR) sensor based on a multi-core photonic crystal fiber(PCF) is presented in this paper.There is only one analyte channel positioned in the center of the PCF cross section,rather than several closely arranged analyte channels around the central core.So the design of this sensor not only reduces the consumption of gold and samples,but also effectively avoids the interference between neighboring analyte channels.Optical field distributions of this fiber at different wavelengths and the sensing properties of this sensor are theoretically analyzed and discussed using finite element method(FEM).Simulation results confirm that both the thickness of metallic layer and the fiber structural parameters have significant effect on sensing performance.The amplitude sensitivity of the sensor is found to be 1.74×10-5RIU,and the spectral sensitivity is 3300 nm/RIU,corresponding to a resolution of 3.03×10-5 RIU.Finally,in order to achieve PCF-SPR sensing characteristics,an experiment design scheme based on spectroscopic detection method is proposed.     

Optical Refractive-Index Sensor Based on Dual Fiber-Bragg Gratings Interposed With a Multimode-Fiber Taper

A new type of optical refractive-index (RI) sensor is proposed and experimentally demonstrated by using a structure of two single-mode fiber (SMF) Bragg gratings with a multimode fiber (MMF) taper in-between. The loss induced by a mismatch of waveguide structure between SMFs and MMFs is amplified by a tapering process, and is utilized for RI sensing through evanescent field. Experimental results show that the sensor possesses a tailorable sensitivity to the change of external RI and has a good linear response in the simultaneous measurement of external RI and temperature     

Modeling of Tapered Fiber-Optic Surface Plasmon Resonance Sensor With Enhanced Sensitivity

Theoretical model for surface-plasmon-resonance-based fiber-optic sensor with a metal-coated uniform core sensing region sandwiched between two identical tapered fiber regions is proposed. The effect of taper ratio (TR) on the sensitivity of the sensor is studied. The study shows that the proposed probe geometry with TR lying between 1.5 and 2.0 provides the best performance. The physical reasons behind sensitivity enhancement due to tapered regions are provided.