Quasi-distributed strain sensing with white-light interferometry: a novel approach

An optical fiber ring is used to generate multiple reference waves in a multiplexed fiber-optic Michelson-type sensor array. The array consists of N sensing segments connected in series along a single optical fiber path and is interrogated with a white-light interferometric technique. Experimental results with a two-sensor array are presented.     

基于白光干涉的光缆无损伤识别方法

提出一种基于白光干涉的光缆无损伤识别方法.将光纤的两端环接,入射光波经耦合器分成两束光,以相反的方向在同一根光纤中传播,用探测器接收另一端产生的信号.在外加作用力下,对并列在一起的两根光纤产生的光程变化进行了理论分析,推导出光缆识别系统输出信号的理论表达式,对系统输出的信号进行了仿真计算.分别利用冲击信号、正弦信号、音...     

使用光纤白光干涉仪测一维形变实验

光纤白光干涉仪是使用波长为1310 nm的半导体发光二极管的相位调制型光纤传感器,可用于压力、温度和应变的测量.本文介绍了光纤白光干涉仪的工作原理,设计了一维形变实验.     

激光调制参数对光纤环型谐振腔光谱特性影响

谐振光学环型腔作为光学陀螺的核心敏感单元,其光学调制谱和与之对应的鉴频曲线的特性成为提高光学陀螺系统检测灵敏度的关键。为了研究光学陀螺的调制和鉴频谱线特性,优化陀螺性能,设计并搭建了实验测试系统,光纤环形谐振腔采用分光比为50∶50、直径17 cm的保偏光纤,总长2.2 m。使用直流高压放大器扫描窄线宽激光器（线宽小于1 kHz）的压电转化模块,扫描频率和电压分别选取20 Hz和1 V,使用模拟比例积分电路进行锁频并反馈给激光器的压电转化模块,使激光器的输出频率跟踪谐振腔实时变化。研究分析了光纤环型谐振腔在两种情况下所对应的透射谱和鉴频曲线：第一种情况为调制电压分别为2 V和4 V,对应调制频率从100 kHz到4 MHz变化;第二种情况为当调制频率为900 kHz,调制电压从2 V到10 V变化。通过实验,得到了不同调制参数下光学陀螺谱线的谐振深度、半高全宽、线性带宽、动态范围、品质因数、标度因数以及对应的锁频精度七种物理量的详细变化情况,并进一步得到了静态测试条件下三种陀螺的最佳调制频率及与之所匹配的调制电压。为进一步研究激光调制对光纤环型谐振腔光谱的影响提供指导。     

激光调制参数对光纤环型谐振腔光谱特性影响

谐振光学环型腔作为光学陀螺的核心敏感单元,其光学调制谱和与之对应的鉴频曲线的特性成为提高光学陀螺系统检测灵敏度的关键。为了研究光学陀螺的调制和鉴频谱线特性,优化陀螺性能,设计并搭建了实验测试系统,光纤环形谐振腔采用分光比为50∶50、直径17 cm的保偏光纤,总长2.2 m。使用直流高压放大器扫描窄线宽激光器（线宽小于1 kHz）的压电转化模块,扫描频率和电压分别选取20 Hz和1 V,使用模拟比例积分电路进行锁频并反馈给激光器的压电转化模块,使激光器的输出频率跟踪谐振腔实时变化。研究分析了光纤环型谐振腔在两种情况下所对应的透射谱和鉴频曲线:第一种情况为调制电压分别为2 V和4 V,对应调制频率从100 kHz到4 MHz变化;第二种情况为当调制频率为900 kHz,调制电压从2 V到10 V变化。通过实验,得到了不同调制参数下光学陀螺谱线的谐振深度、半高全宽、线性带宽、动态范围、品质因数、标度因数以及对应的锁频精度七种物理量的详细变化情况,并进一步得到了静态测试条件下三种陀螺的最佳调制频率及与之所匹配的调制电压。为进一步研究激光调制对光纤环型谐振腔光谱的影响提供指导。     

集磁式光纤电流传感器的研究

设计了一种应用块状磁光材料与集磁环相结合的集磁式光纤电流传感器。介绍了该传感器的结构及工作原理,构建了光纤电流传感器实验系统并进行了测试。实验结果表明,该集磁式光纤电流传感器在30kV工作电压下可准确实现30kA脉冲或连续电流的测量,为电力系统中高压大电流测量提供了一种切实有效的方法。     

Sapphire-fiber-based white-light interferometric sensor for high-temperature measurements

We present a fiber-optic temperature sensor with a single-crystal sapphire fiber as the light guide and a sapphire wafer as the sensing element. Temperature is determined by measurement of the thermal dependence of the wafer's optical thickness by use of white-light interferometry. We applied digital signal processing techniques to analyze the sensor's spectrum. A prototype sensor was tested to 1600 degrees C and demonstrated excellent reproducibility. An accuracy of +/- 0.2% full scale was obtained. The sensor is simple, small, and flexible, with potential advantages of batch fabrication and easy calibration.     

Berry's phase amplification by a ring resonator

It is shown that, similar to resonant enhancement of linear phase, birefringent phase, and chirality/optical activity by a ring resonator (RR), Berry's phase, or the geometrical phase, can be amplified by repeatedly passing light through a Berry's phase-generating element placed in a RR. Small-signal amplification of Berry's phase is equal to the resonator finesse F. This amplification can be exploited when Berry's phase is used for performing quantum computation or in fiber-optic and other sensors.     

Demodulation algorithm for spatial-frequency-division-multiplexed fiber-optic Fizeau strain sensor networks

A demodulation algorithm for spatial-frequency-division-multiplexed fiber-optic Fizeau strain sensor networks with a large number of sensors is proposed to effectively reduce the cross talk between any two adjacent sensors and hence substantially enhance the multiplexing capability of the network, which is based on the Pisarenko algorithm. The cross talk between two fiber-optic Fizeau sensors is investigated experimentally. The experimental results show that a strain accuracy of better than +/-10 micro permittivity can be achieved even when the cavity length difference is approximately 100 microm. It was demonstrated that the multiplexing capability of the spatial-frequency-division-multiplexed fiber-optic Fizeau sensor network can be approximately 5 times greater than that of the conventional fast-Fourier-transform algorithm, and this can lead to achievement of a sensing network with a multiplexing capability of as many as 1000 Fizeau sensors.     

Tunable Fabry-Perot-resonator-based fiber-optic white-light interferometric sensor array

A tunable Fabry-Perot-resonator-based fiber-optic white-light interferometric quasi-distributed sensing system permitting absolute length measurement in a remote reflective sensor array is proposed and demonstrated. The sensor reflective signals characteristics have been analyzed, and the relationship between light signal intensities and sensors number was given for multiplexing potential evaluation. The proposed sensing scheme will be useful for the measurement of strain distribution. An important application could be deformation sensing in smart structures. Experimentally, a four-sensor array has been demonstrated.     

Design of ring resonator based all optical switch for logic and arithmetic operations – A theoretical study

In this paper, a general analysis for non-linear micro-ring resonator as all optical switch is discussed in a vertically coupled GaAs–AlGaAs micro-ring resonator by carrier injection. The ring resonator is optically pumped, which results in temporal shift of resonant wavelength by refractive index change due to carrier injection. A green laser as optical pump beam is used to shift resonant wavelength 1.5 nm of the ring resonator. Simulation, analysis and overall transfer function of single ring as well as cascaded micro-ring resonator (MRR) is studied. A single circuit, consisting of three MRRs, capable to perform all the two input sixteen logic operations is studied and reported. The same circuit can also act as half adder/subtractor and single bit data comparator.     

垂直扫描白光干涉术用于微机电系统的尺寸表征

随着微机电系统的发展,器件设计和加工过程中的表征成为一个主要问题。提出了将扫描白光干涉表面轮廓测量方法用于微结构和器件的几何特性检测上。测量系统采用了米劳显微干涉仪,利用压电陶瓷物镜纳米定位器实现垂直方向100μm范围内的精确扫描,并通过傅里叶变换算法获取条纹包络峰的位置,进而得到器件的整体集合尺寸信息,与相移干涉方法相比大大提高了测量范围。通过测量纳米台阶对该系统进行了精度标定,测量重复性在亚纳米量级。最后通过测量微谐振器和微压力传感器的几何尺寸说明了该方法的功能。     

光纤菲佐传感器频分复用网络解调方法研究

为了减小光纤菲佐传感器间的串扰,提高传感器网络的复用能力,提出了基于Pisarenko正弦波恢复法的光纤菲佐应变传感器频分复用网络光谱解调方案。在多光束干涉原理的基础上,建立了基于Pisarenko正弦波恢复方法的传感器频分复用解调模型,并对2个光纤菲佐传感器的串扰进行了实验研究。快速傅里叶变换能够达到应变精度好于±10με的传感器间最小腔长差约为500μm,而该方法可以把最小腔长差缩短至100μm左右。这意味着系统的复用能力提高了大约5倍。因此,该方法是一种串扰小、复用能力强的解调方法,在大容量准分布式传感网络中具有极大的潜在应用价值。     

分布式光纤温度传感技术在隧道监测中的应用

介绍了分布式光纤温度传感检测原理及采用拉曼散射型分布式光纤温度传感器并将其与高速采集处理电路集成的检测方式。分析了分布式光纤温度传感技术应用于隧道火情监控的优越性。结合计算机及现场Modbus网络构建了隧道监测网络，同时还介绍了开发隧道监测网络的软硬件设计过程。现场实验表明，分布式光纤温度传感技术具有良好的应用前景和较高的推广价值。     

High-speed wavelength-swept semiconductor laser with a polygon-scanner-based wavelength filter

Ultrahigh-speed tuning of an extended-cavity semiconductor laser is demonstrated. The laser resonator comprises a unidirectional fiber-optic ring, a semiconductor optical amplifier as the gain medium, and a novel scanning filter based on a polygonal scanner. Variable tuning rates up to 1150 nm/ms (15.7-kHz repetition frequency) are demonstrated over a 70-nm wavelength span centered at 1.32 microm. This tuning rate is more than an order of magnitude faster than previously demonstrated and is facilitated in part by self-frequency shifting in the semiconductor optical amplifier. The instantaneous linewidth of the source is <0.1 nm for 9-mW cw output power and a low spontaneous-emission background of -80 dB.     

The narrow band THz filter in metallic photonic crystal slab framework: Design and investigation

A band pass THz filter has been presented by the aid of coupling between the waveguides and ring resonator based on metallic photonic crystal slab. The rows of rods are missed and remaining rods in the rows play as a reflector then the position of central rods are rearranged as a ring, the radius of reflector rods and ring resonator is modified in order to optimize the resonance frequency and Q-factor. In addition, 3D-FDTD method is used for simulation results. One of the predominant features of the proposed structure for THz filter is its capability of obtaining a Q-factor of about 333 in the 1 THz resonance frequency with the normalized peak transmission of higher than 0.7, because of high Q-factor cavity based on ring resonator.     

Vertical input optical ring resonator with differential operation for optical sensor

A novel waveguide ring resonator optical sensor with two resonant wavelength channels is proposed for a refractive index measurement of a test sample placed on the sensor substrate and its performance characteristics are investigated analytically and numerically. The waveguide device consists of a ring resonator, a split-ring-shaped loop waveguide, and a vertical input/output grating coupler, in which the loop waveguide acts as an additional resonator and provides another output wavelength channel of the sensor. The differential detection between the two wavelength channels enables the highly sensitive detection with temperature compensation. A numerical simulation based on a finite difference time domain (FDTD) method shows that a precise index change detection with a resolution of 10⁻⁶ can be achieved using of the proposed device.     

A tunable hybrid graphene-metal metamaterial absorber for sensing in the THz regime

In this paper, a graphene-based metamaterial absorber is proposed and investigated numerically, in which the interaction between a split ring resonator (SRR) and graphene results in a high-Q absorption. To make a better understanding of the resonance mechanism, the electric and the magnetic fields, and the surface currents at the resonance frequency are investigated. In order to ease the analysis of the structure, an equivalent circuit model is introduced using the transmission line theory, and the accuracy of the proposed model is verified by the full-wave simulation. Finally, different aspects of the designed metamaterial are discussed as a potential label-free sensor for chemical and biomedical sensing. It is shown that by using this structure, a sensor with a sensitivity of 597 GHz/RIU can be achieved.     

Liquid-core optical ring-resonator sensors

We have demonstrated a novel sensor architecture based on a liquid-core optical ring-resonator (LCORR) in which a fused silica capillary is utilized to carry the aqueous sample and to act as the ring resonator. The wall thickness of the LCORR is controlled to a few micrometers to expose the whispering gallery mode to the aqueous core. Optical characterization with a water-ethanol mixture shows that the spectral sensitivity of the LCORR sensor is approximately 2.6 nm per refractive index unit. A model based on Mie theory is established to explain the experimental results. The LCORR takes advantage of the high sensitivity, small footprint, and low sample consumption with the ring resonator, as well as the efficient fluidic sample delivery with the capillary, and will open an avenue to future multiplexed sensor array development.     

A nano-scale transducer using a PANDA type ring resonator for gas sensor applications

We present a new system of nano-scale gas sensor using PANDA type ring resonator, whereas the sensing unit is a splitting ring resonator with two and four gaps. The method of finite difference time domain (FDTD) via the computer programming called Opti-wave was used to analyze and simulated all the parameters. The two systems were compared and the simulation result shown that the system of four splitting gaps is better resolution and more linear relationship than two splitting gaps unit. Finally, we found that this system can be used to be a high-precision self-calibration nano-scale gas sensor with in the of resolution of 1 nm.