Fiber-Optic Current Sensor Using Passive Demodulation Interferometric Scheme

An interferometer using a Faraday rotator with 22.5 rotation bias is proposed for the use of a fiber-optic current sensor (FOCS) to demodulate phase signals passively. High sensitivities and extra low distortions are obtained by this passive demodulation interferometric scheme (PDIS). The Verdet constant of optical fibers at 1300 nm is evaluated to be 4.5 murad (A rms.turns), which is in good agreement with the literature. With signal distortions always below 0.8 %, the proposed scheme should be significantly effective for the demodulation needs of an FOCS. The PDIS also could enable a FOCS to directly connect with fiber-optic communication networks for the implementation of long-distance remote and multiplexing sensor systems. Moreover, electric shock concerns on current intensity measurements of high-voltage power delivery systems are greatly reduced.     

Stable RF transfer over a fiber-optic ring with DSBCS modulation and a DSB RF signal

We propose a radio frequency(RF)transfer technique with passive phase noise compensation over a fiber-optic ring.By adopting different frequencies and same wavelength transmission and double sideband(DSB)with carrier suppression(DSBCS)modulation,the impact of backscattering can be effectively suppressed.A stable RF signal can be obtained via frequency mixing at an arbitrary access site along the fiber-optic ring.As the two directional transmissions adopt the same fiber and same wavelength from the same laser,the bidirectional propagation symmetry can be maximally guaranteed.We experimentally demonstrate 2 GHz RF signal transfer along a 100 km standard single-mode fiber-optic ring.     

Schemes of a fiber-optic multiplexing sensor array based on a 3 X 3 star coupler

A Michelson-based fiber-optic low-coherence interferometric quasi-distributed sensing system permitting absolute length measurement in a sensor array is proposed. The main part of the sensing system is a fiberoptic 3 x 3 star coupler. The architecture of fiber-optic sensors can be easily realized as a linear sensor array, twin sensor arrays, or a loop sensor array. The proposed sensing scheme will be useful for the measurement of strain distribution. An important application could be deformation sensing in smart structures. A six-sensor array is demonstrated experimentally.     

Characterization of a scintillating fiber-optic dosimeter for photon beam therapy

Abstact  A scintillating fiber-optic dosimeter has many advantages such as real-time readout, high-resolution measurement, water-equivalence and no corrections for temperature, pressure and humidity. Organic scintillator which has water or tissue equivalent characteristics is very important to measure absorbed dose, dose rate and dose distributions exactly without any corrections and due to its small size, the sensitive volume enables accurate dose measurements in regions of high dose gradients with high spatial resolution. In this study, a scintillating fiber-optic dosimeter with an organic scintillator is fabricated to measure high-energy photon beam from a clinical linear accelerator. And we have measured linear responses of a fiber-optic dosimeter according to dose rates and monitor units of a clinical linear accelerator. Also, a percent depth dose curve for 6MV photon beam with different field sizes are obtained.     

光纤化学传感技术研究近况

光纤化学传感器作为传感器的一个重要分支,结合了化学和光学的相关技术,将化学制膜、光纤技术以及化学分析中的分光光度法、拉曼光谱、荧光光谱、折射率检测等方法相融合,以其微型化,抗电磁干扰,传输信息量大,拥有自身参比等特点不断向前发展。简要综述了光纤化学传感技术研究近况和未来的发展趋势。重点对光纤pH化学传感器、光纤离子化学传感器和光纤气体化学传感器进行了介绍。简要分析了常见的敏感膜制备方法如化学键合法和溶胶凝胶(sol-gel)等方法。新型光纤——微结构光纤的出现为光纤化学传感器开辟了新的发展方向。由于其具有大的内表面积,结构设计灵活多样,光纤内部提供感应场所等特点,快速度成为光纤化学传感器的重要发展方向和研究热点。对微结构光纤衍生而来的新型光纤化学传感器进行了详细评述, 最后对光纤化学传感器的未来进行展望。     

Finite-Element Model of a Fiber-Optic Polarizer

Numerical analysis of the vector modes of a fiber-optic polarizer is performed by the finite-element method. The calculation results are compared with the data obtained using a planar model.     

Chaotic synchronization via linear controller

A technical framework of constructing a linear controller for chaotic synchronization by utilizing the stability theory of cascade-connected system is presented. Based on the method developed in the paper, two simple and linear feedback controllers, as examples, are derived for the synchronization of Liu chaotic system and Duffing oscillator, respectively. This method is quite flexible in constructing a control law. Its effectiveness is also illustrated by the simulation results.     

Analysis of a fiber ring resonator as a multi-path light-wave circuit in white-light fiber-optic interferometric sensors

According to the phase shift response of a ring resonator, the role of a fiber-optic ring resonator as a multi-path light-wave circuit in white-light fiber-optic interferometric sensors is analyzed. Formulas related to the maximum intensity of the interference fringes and the system parameters are derived by exact mathematic deduction. The main factors affecting the multiplexing capability of the sensor array are discussed. The analysis method not only gives an explicit explanation for the enhancement of multiplexing capability but also can be applied to other structural white-light sensor systems, in which the ring resonator is used as a multi-path light-wave circuit.     

一种高稳定、高分辨率的光纤位移检测系统

介绍一种大量程、高分辨率、高稳定的光纤传感位移测量系统。该系统基于反射式强度调制机制,由光发射机、传感器、光接收机三部分组成。系统通过采用调制、解调、窄带滤波,信号支路和参考支路双通道相比测量等技术措施,来保证系统的高稳定性和高分辨率。实验还表明测量中应尽量使用朗伯特平面作为光反射面,以解决二次安装的重复性问题。     

Fiber-optic hydrophone using a cylindrical Helmholtz resonator as a mechanical anti-aliasing filter

Two Michelson interferometric fiber-optic hydrophones that use panda polarization-maintaining fibers and devices have been constructed and tested. The low-frequency acoustic sensitivities of both hydrophones are -159 dB re 1 rad/microPa. One of the hydrophones tested has a small cylindrical Helmholtz resonator that has a break point near 1200 Hz and a measured roll-off of approximately 50 dB/octave, and it is a hydrostatic-pressure-insensitive design. This hydrophone is a prototype device for a class of sensors that can be used to eliminate aliasing in future sonar systems. To our knowledge, this is the first time that such a fiber-optic hydrophone has been reported.     

Analysis of bias thermal stability of interferometer fiber-optic gyroscope using a solid-core polarization-maintaining photonic crystal fiber

Bias thermal stability of a fiber-optic gyroscope using polarization-maintaining photonic crystal (PM-PCF) was studied. The thermal sensitivity of birefringence in PM-PCF and polarization cross talking in fiber coil was measured. Using an OCDP method, the polarization cross talking causing phase error of the fiber-optic gyroscope (FOG) was analyzed. The contrast experiment result of the FOGs with the PM-PCF coil and PMF coil showed that using PM-PCF instead of PMF can improve the FOG’s bias thermal stability by about 50 %.     

光纤型偏振器消光比测试方法研究

介绍了单模光纤偏振器和保偏光纤偏振器 (包括研磨型保偏光纤偏振器和线圈型保偏光纤偏振器 )消光比的基本测试方法。单模光纤偏振器的基本测试方法有偏振控制器法和旋转波片法 ;研磨型保偏光纤偏振器的基本测试方法有起偏器 45°法和消偏法 ;线圈型保偏光纤偏振器的基本测试方法有偏振控制器法和消偏法。对每种方法的优点和缺点以及在测试过程中可能会出现的问题进行了详细分析 ,并通过实验进行了验证     

一种具有声低通滤波特性的无源零差光纤水听器

报道了一种新颖的具有抗混叠功能的无源零差迈克耳孙型光纤水听器.它由一个普通的芯轴型光纤水听器和一个圆柱型亥姆霍兹共振器构成.在驻波罐中对其声压相位灵敏度频响进行了测量,结果表明该光纤水听器具有较好的声低通滤波特性,能有效地抑制声信号中的高频成分,从而实现抗混叠滤波.该光纤水听器的低频声压相位灵敏度主要由传感光纤长度和弹性增敏层的物理特性决定,约为-159 dB(0 dB=1 rad/μPa).在1150 Hz附近出现了一个共振峰,这主要由圆柱型亥姆霍兹共振器的声学特性决定.1150～2280 Hz频段内的灵敏度衰减率约为50 dB/倍频程,1500 Hz以后的灵敏度衰减量大于10 dB.这对于提高我国未来声纳系统的抗干扰能力具有十分重要的意义.     

光缆弯曲对激光能量传输效率的影响

研究了激光火工品系统中光缆弯曲对激光能量传输效率的影响.对7种不同规格光缆在弯曲半径R为2.5~175 mm范围内的弯曲传输特性进行了试验研究.结果表明,R/2a＜50 时,透光量已开始下降;R/2a≈20 时,激光能量传输效率明显下降.根据实验结果,通过数据拟合处理得出了7种规格光缆弯曲损耗的半经验公式,该公式可以直接用于激光火工品系统光缆的传输设计.     

两种光纤探针在冲击波作用下的时间响应特性

 对冲击波参数的测量开发了两种光纤探针，以满足强电磁环境和冲击压力较低的情况。一种是冲击自发光光纤探针，另一种是闪光隙光纤探针。这两种光纤探针分别利用融凝石英在受到冲击压缩时发光和氩气（或空气）隙在受到压缩时会产生很强的光辐射的机理研制而成的。自发光光纤探针在大于70 GPa冲击压力下，其信号上升时间在1~3 ns之间；闪光隙光纤探针在10～30 GPa的冲击压力下，其信号上升时间稳定在2~7 ns之间。     

二阶声低通滤波光纤水听器的声压灵敏度频响特性

信号混叠是基于光纤水听器的现代声纳系统走向应用必须解决的一个关键问题.初步的实验结果已经表明,声低通滤波光纤水听器是解决信号混叠问题的一种简单且行之有效的方案.基于电一声类比理论,建立了声低屯瞬ü庀怂鞯牡推导胁瘟磕Ｐ?利用电路分析的方法对其频响特性进行了研究.结果表明,这种光纤水听器系统与典型的二阶低通滤波电路具有相似的频响特性.为了验证理论分析的正确性,设计制作了一个简单的声低通滤波光纤水听器,并在驻波罐中对其声压灵敏度频响特性进行了测试,实验结果与数值计算的结果基本吻合.该光纤水听器低频响应非常平坦,声压灵敏度约为-141 dB,测量共振频率为985 Hz,与理论值1270 Hz基本一致.共振频率处的声压灵敏度为-126.8 dB,衰减速率约为20 dB/倍频程,3000 Hz以后的灵敏度衰减幅度大于20 dB.     

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。     

Feasibility study on fiber-optic goniometer for measuring knee joint angle

In this study, we fabricated a fiber-optic goniometer using a plastic optical fiber, a light-emitting diode, and a photodiode. The cladding of the plastic optical fiber was removed at 0.5–3mm intervals regularly to increase the bending loss of the plastic optical fiber. Also, the output voltages of the photodiode based on light intensity that measured using the fiber-optic goniometer were measured light intensities using the fiber-optic goniometer were measured to evaluate the linearity of the fiber-optic goniometer. Finally, we measured the responses of the fiber-optic goniometer for gait speeds of 3, 5, and 10 km/h using a data acquisition board and a LabVIEW program.     

Optical multiplexing of microcavity sensors based on a fiber laser

A new principle of creating multiplex systems of active oscillator microcavity fiber-optic sensors is considered. The results of experimental studies of a multiplex system with two measuring channels are presented.     

用光纤探针测量飞层前界面状态的初步探索

 对用光纤探针测量飞层前界面微喷、微层裂等现象的机理进行了分析,设计了光纤探针与瞬态粒子场全息照相技术联合测量泰安药柱加载下铅飞层的前界面状态的实验。实验结果表明,光纤探针的测量结果与瞬态全息照相的结果相吻合,说明利用光纤探针可以对微喷粒子场进行有效探测,是一种很有发展潜力的测试技术。