Multimode Fiber Devices for Optical Fiber Links, Printing, and Display

It is generally agreed that multimode graded index fiber has become the main fiber technology for optical communication applications. Multimode graded index fibers provide sufficient bandwidth for most applications without the critical tolerances of single mode fibers. In this paper, multimode fiber devices and components based on packaging miniaturized optical components for a GaAs laser array source package, and multichannel waveguides will be discussed. Experimental results, fabrication process and technology limitation for some of the multimode devices will be included. One major drawback of using multimode fibers is the difficulty to obtain simple and efficient switches and taps which are essential for data bus or other optical links. Some possible solutions for multimode fiber switches with miniaturized bulk wave devices will be presented.     

基于双金属膜的光纤MEMS温度传感器的设计

提出了一种新型结构的温度传感器,该传感器基于Fabry-Perot干涉和双金属效应.采用MEMS技术制作出线性度好、精度高的光纤MEMS温度传感器.阐述了传感器的工作原理,研究了传感器的力学模型,确定了温度敏感膜材料,用有限元软件ANSYS验证了模型的合理性.模拟了法珀腔的腔长对温度传感器性能的影响,为传感器的加工制作提供了理论依据.该设计可为以硅为基底的压力传感器提供一种温度补偿方法.     

基于MEMS技术的水平轴光纤加速度传感器

提出了一种基于微机电系统(MEMS)技术的水平轴光纤加速度传感器,并与Z轴光纤加速度传感器在同一MEMS芯片上制造,形成单一方向出纤的三轴光纤加速度传感器。分析了器件工作原理和器件结构参数与其性能的关系,利用MEMS技术成功制作出了加速度传感器样品。初步测试结果表明,本光纤加速度传感器灵敏度为164mV/g,3dB带宽的截止频率为1 600Hz。     

Design of distributed Raman temperature sensing system based on single-mode optical fiber

The distributed optical fiber temperature sensor system based on Raman scattering has developed rapidly since it was invented in 1970s. The optical wavelengths used in most of the distributed temperature optical fiber sensor system based on the Raman scattering are around from 840 to 1330 nm, and the system operates with multimode optical fibers. However, this wavelength range is not suitable for long-distance transmission due to the high attenuation and dispersion of the transmission optical fiber. A novel distributed optical fiber Raman temperature sensor system based on standard single-mode optical fiber is proposed. The system employs the wavelength of 1550 nm as the probe light and the standard communication optical fiber as the sensing medium to increase the sensing distance. This system mainly includes three modules: the probe light transmitting module, the light magnifying and transmission module, and the signal acquisition module.     

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。     

Temperature and refractive index sensing characteristics of an MZI-based multimode fiber–dispersion compensation fiber–multimode fiber structure

We proposed an optical fiber sensor with simple multimode fiber (MMF)–dispersion compensation fiber (DCF)–multimode fiber structure based on Mach–Zehnder Interferometer (MZI) and researched its temperature and refractive index (RI) sensing characteristics. The sensing principle is based on the interference between core and cladding modes of DCF due to the large core diameter mismatch. Spectral analyses demonstrate that the transmission spectrum is mainly formed by the interference between the dominant excited cladding mode and core modes. The experimental results show that the proposed sensor has high temperature sensitivity of 0.118 nm/°C in the range of 20–250 °C and RI sensitivity of 66.32 nm/RIU within the linear sensing range of 1.33–1.39 RIU. Therefore, the characteristics of compact size, low cost, easy fabrication, high sensitivities, and good anti-interference ability make this sensor have extensive application prospects.     

基于纤芯失配多模干涉的光纤折射率传感器

基于多模干涉效应的单模-多模-单模(SMS)结构光纤折射率传感器通常需要进行包层腐蚀来提高灵敏度,而且易受环境温度影响。为克服SMS结构的这些不足,提出了一种新型的基于纤芯失配多模干涉的光纤折射率传感器,由单模光纤-色散补偿光纤-单模光纤(SMF-DCF-SMF)级联光纤布拉格光栅(FBG)构成,长度不超过100mm。对其灵敏度、线性范围和温度特性等进行了测试,实验结果显示在测量折射率为1.33～1.39的折射率液时,特征波长与折射率呈线性关系,灵敏度为232.8nm,级联的FBG具有良好的温度校准功能。     

Propagation of the fundamental mode in curved graded indexmultimode fiber and its application in sensor systems

A novel principle of light transmission through very small radius bend in optical fibers is presented. The potential applications of the proposed structure are fiber optic sensors and other fiber optic systems. The design makes use of graded index multimode fiber as transmission medium. However, the feed to the multimode fiber is through a single mode 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 fundamental mode within graded index multimode fiber proves to be very insensitive to macrobends if bend radius is larger than certain critical value. If bend radius is reduced below critical value the loss increases very rapidly and this allows for construction of relatively sensitive macrobend fiber optic sensor. This work presents a quantitative theoretical model of the proposed structure and a detailed experimental investigation of structure with possibilities for its practical applications     

F-P腔式光纤MEMS压力传感器的设计

提出了一种新型结构的法布里-珀罗(F-P)腔光纤压力传感器.该传感器基于法布里-珀罗多光束干涉,利用压力敏感膜的纵向挠度变化带动位移柱的横向位移运动来改变F-P腔的腔长变化.详细阐述了传感器新结构的设计方法及其工作原理,分析了不同参数对传感器性能的影响.采用ANSYS软件仿真模拟了传感器压力敏感膜在压力作用下的挠度变化.结合现有的MEMS工艺,可制作出工艺简单、温度系数低、灵敏度高,且抗电磁干扰的MEMS光纤压力传感器.     

毛细石英管构成的高灵敏度光纤气压传感器

为实现高精度的气压测量,提出一种利用飞秒激 光微加工技术与光纤熔接技术制作的法布里- 珀罗(FP)干涉仪(FPI)型光纤气压传感器。利用波长800nm的飞秒 激光脉冲在毛细石英管侧壁上加工一微孔, 利用光纤熔接技术把毛细石英管熔接在一段单模光纤(SMF)和一段多模光纤(MMF)之间,制备 出一种光纤气压传 感器。通过改变传感器的FP腔内气压大小,导致FP腔内气体折射率改变,从而引起传感器 的透射 谱线性漂移,通过计算气压变化量与透射谱的谐振峰波长漂移量之间的关系就能够实现传感 器的气 压测量。理论分析了传感器实现气压测量的机理,实验测量了传感器的灵敏度。实验结 果表明, 传感器对周围气压变化的响应较大,透射谱的谐振峰波长随气压线性变化的灵敏度达到4.22nm/Mpa,而传感器对环境温度变化的响应很小,减少了温度对气压 测量的交叉感染。     

基于单侧几何形变结构的全光纤Michelson干涉高温传感器

利用CO2激光脉冲对标准单模光纤(SMF)单向形成较小的几何形变,把部分基模能量耦合到光纤包层,制作了一种新型的在线型Michelson干涉传感器。理论分析了这种几何微扰激发的包层模特性,并利用芯模-包层模较大的热光系数差,把这种传感器应用于高温测量。实验结果表明,这种干涉传感器的温度灵敏度为0.093 7nm/℃,并且在800℃温度范围内具有良好的线性和重复性。这种制作简单、结构稳定、体积小和灵敏度高的全光纤在线型Michelson温度传感器将具有较大的潜在应用价值。     

差动式光纤微弯传感器

设计了一种新型的差动式光纤微弯传感器,并对传感器的位移特性和应变特性进行了实验研究。该传感器的特点是不仅可以测量位移、应力、应变等参量的大小,还可以判断参量的方向,且灵敏度比单一传感器增加一倍。实验证明,通过在传感器中加入变形齿限位装置和光纤定位槽,大大改善了差动式光纤微弯传感器的敏感性能和实用性。     

基于保偏光子晶体光纤的高灵敏度曲率传感器

为了能高精度测量小曲率,采用单模-鼓包-保偏光子晶体光纤-多模-单模光纤组成的结构,其中多模光纤和单模光纤之间错位熔接。通过理论分析和实验验证得到在0.04582m-1~0.054776m-1及0.054776m-1~0.06929m-1曲率范围内,谐振波长漂移与曲率变化之间分别存在着线性关系。结果表明,该曲率传感器灵敏度值分别为93.95nm/m-1和30.89nm/m-1,可以应用于健康监测等需要测量小曲率的场合。     

差动式光纤微弯传感器

设计了一种新型的差动式光纤微弯传感器，并对传感器的位移特性和应变特性进行了实验研究。该传感器的特点是不仅可以测量位移、应力、应变等参量的大小，还可以判断参量的方向，且灵敏度比单一传感器增加一倍。实验证明，通过在传感器中加入变形齿限位装置和光纤定位槽，大大改善了差动式光纤微弯传感器的敏感性能和实用性。     

Sensitivity-enhanced fiber optic temperature sensor with strain response suppression

A temperature sensor based on a multimode–singlemode–multimode (MSM) fiber structure has been proposed and experimentally demonstrated. By utilizing the interference between fiber core and cladding modes, temperature measurement is exploited by monitoring the selected resonant dips shift of the transmission spectrum. A high temperature sensitivity of 50.65 pm/°C is achieved at a certain resonant dip, accompanied by a suppressed strain sensitivity of only 0.587 pm/με. The sensor reveals the advantages of easy fabrication and interrogation, low cost and small axial strain response.     

一种新型金属封装的光纤法珀温度传感器

设计制作了一种金属封装的光纤法珀温度传感器,该传感器采用不锈钢毛细金属管代替传统的空心光纤对光纤法珀腔进行封装,毛细金属管在作为法珀腔腔体的同时也是温度敏感元件。采用该结构简化了光纤法珀温度传感器的封装工艺,理论分析和实验的结果表明,该金属封装结构使得传感器的灵敏度易于控制,对于腔长为10mm的温度传感器其精度达到±0.5℃。     

基于光纤传感技术的光电报警系统

根据微弯式阶跃型多模光纤传感器的基本原理,设计了一种结构简单、体积小、灵敏度高的实用光电报警系统.从理论上分析、设计了使光纤产生微弯曲的梳状变形器,并且计算出报警系统高灵敏度所需的变形器周期,约1.1 mm;另外,设计了与之匹配的报警电路模块.该模块由平衡电桥、电压比较器、单态触发器和多谐振荡器组成,电压比较器根据平衡电桥的状态产生相应的电信号到单态触发器,进而通过单态触发器控制多谐振荡器,实现报警处理,适当调节平衡电桥的变阻器可以改变报警系统的敏感度.     

空芯光纤多模干涉型光纤液位传感技术研究

为了测量液位高度变化,采用基于空芯光纤多模干涉效应的方法,研究了在外界介质影响下光源在空芯光纤中多模干涉所产生的干涉谱的变化,进行了基于空芯光纤中多模干涉效应的液位传感实验,研究了该液位传感器的干涉谱与液位变化的关系以及不同折射率液体对测量结果的影响,并分析了实验误差。结果表明,该光纤液位传感器的液位测量范围为0mm~55mm、液体折射率为1.33和1.35时,液位测量灵敏度分别为0.180nm/mm和0.224nm/mm。使用单模-空芯-单模结构的传感器进行液位变化测量是较为精准与可行的。     

Temperature sensor based on dielectric optical microresonator

An optical temperature sensor has been presented based on Whispering Gallery Mode (WGM) dielectric microresonator. The effect of Transverse Electric (TE) wave propagation in dielectric micro-spheres presented has been for optical resonances based on WGM. TE waves are characterized both theoretically and experimentally for large size parameter of the micro-spheres. A theoretical model has been developed based on asymptotic approach. The theoretical development is mathematically robust and significantly less complicated than existing approaches presented in the literature. The quality factor of experimental resonance spectra observed in the laboratory is calculated approximately in the order of 10⁴ which is sensitive enough to detect micro or nano level temperature changes in the surrounding medium. The sensitivity of the Morphology Dependent Resonance (MDR) temperature sensor is wavelength change of 10⁻⁹ m for one degree centigrade change in temperature. This sensor could potentially be used for nano technology, Micro-Electro-Mechanical Systems (MEMS) devices, and biomedical applications.     

自映像多模干涉仪的应力传感研究

提出一种基于自映像原理的多模应力传感器。通过测量透射谱中满足自映像条件的波峰波长,解调纵向应力的大小。分析了传感器中多模光纤(MMF)结构参数对透射谱的影响。0～4 400με纵向应力范围的实验结果表明,透射光谱峰值波长的漂移与应力之间呈良好的线性关系,应力敏感度为1.29pm/με。本文传感器制备简单,对MMF的长度精度要求不高。利用多模干涉仪(MMI)的带通特性,可以通过简单地并联不同长度的无芯光纤传感器实现多路复用。