一种新型的光子晶体波导

提出了一种新型的能够实现定向辐射的光子晶体波导。数值仿真结果显示这种光子晶体波导具有更好的定向辐射性能。这种结构能够用于提高传统的介质波导和光子晶体波导之间的耦合效率。     

长周期光纤光栅及其在通信传感领域的新应用

长周期光纤光栅是一种新型光纤器件。介绍了长周期光纤光栅的耦合机理、制备方法以及应用。其耦合机理是前向传输的纤芯基模与前向传输的各阶包层模式之间的耦合。制备原理是对光纤横向曝光,使光纤的折射率指数在轴向发生周期性变化。阐明了长周期光纤光栅用于带通滤波、光上下路复用、光纤光源、光纤耦合、偏振器件、新型传感等新技术领域的思路,给出了具体实现方法。并通过与其他方案对比,说明了基于长周期光纤光栅器件的优点,肯定了长周期光纤光栅在通信传感领域的价值。     

34km传感长度的布里渊光时域反射计的设计与实现

布里渊分布式光纤传感器是目前最具应用前景的分布式光纤传感技术之一,其关键是如何检测布里渊散射光信号,布里渊光时域反射计是其中较好的检测方式。针对布里渊散射光信号特点,应用光相干技术来检测布里渊散射光信号。具体采用微波电光调制产生频率可调的参考光,和散射光进行相干检测,根据散射光频移特性,应用电信号处理技术取出布里渊散射光电信号,并采用偏振控制技术来抑制相干检测的偏振相干性,再经过数字信号累加和平均处理,最后得到分布式传感信号。采用光相干检测设计方案实现了布里渊时域反射计分布式光纤传感器,并进行了34km光纤的分布式应变传感实验。     

纤芯失配的光纤Mach-Zehnder折射率传感器

基于Mach-Zehnder干涉仪原理,利用光纤错位熔接技术设计并制作了一种单模光纤-多模光纤-单模光纤-错位熔接点-单模光纤结构的液体折射率传感器。传感器中的多模光纤和错位连接部分充当光耦合器;多模光纤在后面的单模光纤的纤芯和包层中激发出纤芯模和包层模,不同的模式有不同的模式折射率,经中间单模光纤传输到错位熔接点处时,不同模式光之间将产生光程差,经错位熔接点耦合成为导出光纤的纤芯模从而产生干涉。对该传感器输出的干涉光谱中干涉谷功率随外界溶液折射率变化的规律进行了理论分析和实验研究。结果表明：溶液折射率变化为1.358 9~1.392 2时,干涉谱中1 530 nm附近的干涉谷光功率与溶液折射率呈单调递增关系,可用于折射率的测量;折射率变化为1.372 0~1.392 2时,传感器响应曲线具有很好的线性度,线性拟合系数为0.998,对应的灵敏度为252.06 dB/RIU。该传感器制作简单、结构紧凑、成本低、灵敏度高,可用于生物医学领域液体折射率的实时测量。     

光纤传感技术在航空发动机温度测试中的应用

温度测试对于航空发动机设计与研制具有极其重要的意义。航空发动机的测温环境具有高温、高压、高速气流冲击、高转速、安装空间狭小等特点,还要求测温系统具有大量程、高精度和高稳定性的工作性能,可供选择的测温方法非常有限。光纤温度传感器具有体积小、抗电磁干扰、极端环境下的安全可靠和使用灵活等优点,并具有串联复用的准分布式传感能力,在航空发动机温度测试中有很好的应用前景。本文对比总结了基于光纤布拉格光栅、光纤法布里-珀罗、光纤超声和光纤辐射等几类典型的光纤温度传感器的传感原理、制造工艺和技术特点,分析了航空发动机研制中不同对象和场景的温度测试需求,对光纤温度传感技术在航发测温领域中的应用研究现状进行了分类整理和发展水平综述,对其在未来实际应用中存在的不足进行了分析,最后对其在未来研究及应用的发展方向进行了展望,为后续航发测温领域研究及应用提供参考。     

基于水凝胶聚合物波导传感器检测盐酸吖啶黄

多功能化是光纤化学传感器的重要发展方向。为实现该目标,首先通过激光诱导波导自形成技术制备了一种光纤–水凝胶聚合物波导–光纤传感结构,并在水凝胶聚合物波导探针中成功地掺杂了纳米金颗粒。在该结构中,波导与光纤同轴无缝相连,保证了探测光和信号光的高效利用。掺金后的聚合物波导具有丰富的光谱探测能力,利用该波导探针成功实现了对盐酸吖啶黄的吸收、荧光以及拉曼光谱的检测,扩大了波导传感器的应用范围。     

High efficiency slotted photonic crystal waveguides for the determination of gases using mid-infrared spectroscopy

We present the design and analysis of a high efficiency slotted photonic crystal waveguide for gas sensing applications in the mid-infrared wavelength range. We designed the slotted photonic crystal waveguide structure by engineering the interfaces between the input and output slot waveguides and a resonant coupler. Coupling and transmission spectra of the sensor have been modeled using the three-dimensional finite-difference time domain method. The sensing principle is based on the shift of the upper band edge of the sensor output transmission spectrum which arises due to changes in the ambient refractive index. Transmission spectrum and sensitivity of the proposed sensor are analyzed by tuning the radii of the air holes localized on each side of the slot. The results show that a change of the refractive index of the gas by 10^?4 leads to a shift of the upper band edge wavelength by 540?pm which corresponding to a sensitivity of 1720?nm per refractive index unit. The proposed design may be an ideal platform for developing mid-infrared gas sensing devices characterized by high coupling efficiencies and high sensitivities.     

Mini review: Recent advances in long period fiber grating biological and chemical sensors

As an important member of the optical fiber sensor family, long period fiber gratings (LPFG) have attracted increased attention due to their outstanding characteristics. The LPFG is a transmission fiber grating without backward reflection, and isolation is not required in the sensing system. The resonant wavelength and transmissivity of LPFGs are very sensitive to changes in refractive index, temperature, strain and transverse load, so they are widely used. In this article, recent advances in biological and chemical applications of LPFG sensors are described. Various methods for improving the sensitivity of LPFG sensors are summarized, such as reducing the diameter of the cladding and cascading. In addition, an important method involves the coating of the LPFG sensor with a specific recognition element for biomass detection or a sensitive metal film for chemical detection. The structural parameters and principles in the literature are discussed in detail. This article analyzes and compares the progress and deficiencies in the detection process and anticipates future developments.     

法布里-珀罗型光纤应变干涉仪

光纤传感技术是现代通信的产物,是随着光纤及通信技术的发展而逐步发展起来的一门崭新技术。光在传输过程中,光纤易受到外界环境的影响,如温度、压力等,从而导致传输光的强度、相位、频率、偏振态等光波量发生变化。通过监测这些量的变化可以获得相应的物理量。详细介绍了一种常用的干涉型光纤传感器——法布里-珀罗（F-P）光纤应变干涉仪。     

干涉型分布式光纤传感系统抗偏振衰落性能研究

为了解决分布式光纤传感系统中常出现的偏振衰落现象,提高系统的稳定性,在分析了系统检测原理基础之上,基于单模光纤的双折射等效琼斯矩阵,建立了分布式光纤传感系统模型,明确了采用不同反射器件条件下,探测光强I与入射光偏振角度i的关系。通过试验证明系统采用旋转角为π/2的法拉第旋转镜(FRM)具有较好的抗偏振衰落特性。     

可调谐光滤波器的研究进展

可调谐光滤波器在光纤通信及光纤光栅传感中发挥了重要的作用。对几种常用的可调谐光滤波器的原理、结构、性能和用途分别进行了介绍,最后给出了其发展趋势。     

Zigzag pattern of Brillouin OF sensor for spatial resolution enhancement

Brillouin optical fiber (OF) sensing technology shows superior potential for structural health monitoring with the advantages of distributed strain and temperature measurement, immunity of electromagnetic interference and so on. However most of current commercial Brillouin OF sensing systems have encountered spatial resolution bottleneck, which cannot deal with local high-precision measurement. A zigzag pattern of Brillouin OF sensor is developed explicitly for spatial resolution enhancement in this paper, and a relative zigzag optical fiber sensor is produced and packaged by fiber reinforced polymer (FRP). Their characteristics are studied by using the strain measurement of one small-size uniform strength beam. From the experiments, the zigzag pattern exhibits excellent performance for strain measurement with high-precision and enhances the spatial resolution to a certain degree without changing the Brillouin sensing instrument’s performance itself.     

Computational analysis of responses of a wedge-shaped-tip optical fiber probe in bubble measurement

Optical-fiber probing is widely employed in bubble∕droplet measurement in gas-liquid two-phase flows. Several types of optical fiber probes with a very high S∕N ratio and high performance have been developed, but further improvement in the probes' measurement accuracy and reliability for industrial applications is desired. We tried to eliminate optical noise in the probe measurements, and we found that the signals include some peak signs that have potential for advanced measurement with optical-fiber probing. We developed a ray-tracing numerical simulator and identified the mechanisms underlying the generation of the signals. In order to numerically simulate the optical probing signals, the simulator must use 3D frameworks composed of incident beams, the reflection and refraction on the surfaces of the optical elements (i.e., an optical fiber, a sensing tip, an air phase, and a water phase), and beams returning from the sensing tip to the other tip through the fiber. We used all of these in a simple rendering framework based on a ray-tracing algorithm with Fresnel's law, and we observed the mechanism of some promising signals that may be useful for extracting the hidden potential of optical-fiber probing. To verify the simulator's performance, we carried out three comparative experiments with fundamental setups using a wedge-shaped single-tip optical fiber probe, examining: (1) the beam trajectories and energy leaking out from the sensing tip into the surrounding air phase or water phase, (2) the probing signals throughout penetration of the sensing tip at the air-water free interface in light of the three-dimensional deformation, and (3) the probing signals throughout penetration of the sensing tip into a bubble in light of the three-dimensional bubble shape. As a result, (a) we found that an optical fiber probe with a wedge-shaped tip has particular characteristics of beam emissions from the tip, and the emitting angles switched depending on the phases covering the tip. This phenomenon is very effective for further advanced measurement. (b) We observed numerically that the cutting angle of the sensing tip maximizing the air signal level was approximately 30°, and therefore this angle is the best for obtaining the highest S∕N ratio. (c) We found that the meniscus shape clearly affected the probing signal optically. (d) We observed the mechanism of a pre-signal caused by the reflection at the frontal and rear interfaces of a bubble. The pre-signal is very useful for practical measurement because it appears only when the probe penetrates the center region of a bubble. We compared the above numerical results with the results of the three experiments, and there was satisfactory correspondence between the numerical and experimental results.     

应用于定位的光纤振动传感技术的发展现状

利用光纤作为传感器提取沿途振动信号,通过对检测信号的处理和分析,可有效地检测和定位发生的故障或入侵行为等。分布式光纤振动传感器利用光波在光纤中传输时相位、偏振等对振动的敏感特性,连续实时地监测光纤附近的振动,并能够定位预防事故,有较好的应用前景。根据传感原理,分布式光纤振动传感技术可分为基于干涉原理和基于后向散射探测技术两类。该文主要从以上两个方面综述分布式振动传感器的主要技术和发展动态。     

光纤传感器在涡轮轴向位移检测中的应用研究

以光纤传感原理为基础，采用一种强度补偿型反射式光纤位移传感器，借助光纤本身的优势，实现涡轮机轴向位移的实时监测。系统包括光源及其驱动电路、光纤传输通道、信号处理电路和信号输出系统。通过双路接收的方法消除因光源发光功率波动、光纤损耗变化以及环境干扰光等因素对测量结果的影响。采用稳压源驱动和温度补偿保证光源发光的稳定性，进行转速监测以补偿速度变化引起的误差。采用单片机完成被测信号的识别和处理，提高了测量的精度。     

Laser-Based Fluorescence Eem Instrument for In-Situ Groundwater Monitoring

I. ABSTRACT

A fluorescence excitation-emission matrix (EEM) instrument is described which employs laser excitation and optical fiber light delivery for remote sensing applications. Ultraviolet laser light is generated at a variety of discrete wavelengths by pumping a Raman shifter with the third or fourth harmonic of a Nd:YAG laser, and this Raman-shifted light is used for fluorescence excitation to generate EEM spectra. Seven-meter optical fibers are used for laser beam delivery and fluorescence light collection, and a diode array detector is used to detect fluorescence emission spectra. As a test of the capability of this instrument, the composition of a two-component mixture of the groundwater pollutants carbazole and p-cresol is determined quantitatively by least-squares analysis of the mixture's fluorescence EEM. Detection limits were in the ppb range and the linear dynamic range was better than 3 orders of magnitude.     

Multiplexing optical fiber low coherence and high coherence interferometric system with large range and high resolution for on-line measurement

A novel optical fiber sensing system multiplexing low coherence interferometry and high coherence interferometry that is endowed with large range and high resolution and is stabilized for on-line measurement is presented. An optical fiber Michelson interferometer performing measurement task in the system works in both modes of low coherence interferometry and high coherence interferometry simultaneously by employing a broadband light source and a fiber Bragg grating as an in-fiber reflective mirror. The amplitude of the measurand is determined by the low coherence interferometry while the value of the measurand is measured by the high coherence interferometry. Another optical fiber Michelson interferometer which is incorporated with the one performing measurement task stabilizes the sensing system for on-line measurement by exploiting an electronic feedback loop to reduce the influences that are resulted from environmental disturbances. The measurement range is 6 mm and the measurement uncertainty is less than 2 nm.     

分布式光纤振动传感器及振动信号模式识别技术研究

研究分布式光纤振动传感技术及光纤振动信号的模式识别技术。通过M-Z干涉原理实现对振动信号的检测,通过信号双向时延定位技术实现光纤振动信号的定位。运用不同的数学方法对光纤振动信号进行分析,找出不同事件产生的振动信号的特征信息,并运用MATLAB进行仿真分析。通过仿真分析,证实了系统能找到挖掘机、车辆及人员走动的特征参数,从而能将这三种不同的事件区分开来。     

基于明胶的光纤湿度传感系统

随着科学的发展,湿度指标在食品安全、仪器制造、生物研究、金属材料等方面备受重视。传统的湿度检测方法以化学方法和电子传感器检测法为主,化学方法对环境有不同程度的污染,而电子传感器检测法的抗电磁干扰能力差,使用环境受限。为解决这些问题,设计了一种新型的光纤湿度传感系统。系统利用明胶薄膜作为湿度传感核心器件,通过搭建传感光路,测量光强变化确定湿度变化。实验验证证明,系统具有良好的湿度传感效果,湿度与光强基本成线性分布,在线性区间内误差小于1.5%,通过进一步优化后可应用于电磁干扰较大环境下的湿度测量。     

基于分布式光纤传感技术的结构变形估计方法研究

悬臂板是广泛应用于工程实践的常见结构形式,在航空航天、轨道交通、土木工程等领域均有重要应用,其变形监测问题一直是此类领域重要的研究内容之一.本文将矩形弹性悬臂薄板纯弯曲的一般问题作为研究对象,讨论求解该问题的方法,建立应变与位移的联系,并在线弹性小变形理论框架下,得到结构横向位移的有限差分表达式;采用具有高密度应变测量...