Remote Temperature Sensor Based on the Up-Conversion Fluorescence Power Ratio of an Erbium-Doped Silica Fiber Pumped at 975 nm

Abstract

This article presents experimental results demonstrating the performance of an erbium-doped silica fiber as a remote temperature sensor in the interval from 20°C to 200°C. The sensor is based on the change in the fluorescence intensity ratio of two spectral bands as a function of temperature. The green fluorescence signal was generated by up-conversion processes in the erbium-doped fiber pumped at 975 nm. A radiometric analysis was applied to the erbium-doped fiber to evaluate its performance as a temperature sensor, and the results from this analysis were compared against other rare-earth-doped fiber sensors that utilize the intensity ratio technique.     

Polymer Optical Fiber Photosensitivities and Highly Tunable Fiber Gratings

In this paper, recent progress in the investigation of photosensitivities of polymer optical fibers and the development of polymer optical fiber grating is reported. Photosensitivities in various polymer fibers, including doped and undoped, multimode and single-mode polymer fibers, have been experimentally characterized and evaluated for fiber grating application. In particular, the wavelength dependence of material absorption and photosensitivity has been found essential to the fabrication of polymer optical fiber grating. Based on the results of photosensitivity research, polymer optical fiber gratings have been successfully fabricated. More importantly, polymer optical fiber grating has been demonstrated highly tunable, with a tuning range more than 70 nm. The unique feature of high tunability in polymer optical fiber grating has great potential in various applications including optical fiber WDM systems and fiber sensor systems. Several important issues that remain to be investigated will also be discussed.     

A Dispersion Flattening Dispersion Compensating Fiber Design for Broadband Dispersion Compensation

An efficient dispersion compensating fiber (DCF) design is proposed based on a coaxial fiber structure, which provides dispersion compensation over a broad wavelength region matching that of an erbium-doped fiber amplifier gain spectrum. The design can provide dispersion coefficient that is nearly twice those of existing DCF designs. Due to the basic nature of the dispersion curve of this design, the total link dispersion cannot only be compensated but also can be flattened.     

Power limitations in fiber-optic frequency-division multiplexed systems

Abstract

Launch power is limited to the milliwatt level by stimulated Brillouin scattering (SBS) in a single-channel, coherent fiber-optic network. Increasing the number of frequency-division multiplexed channels causes the power limit to decrease quickly to submilliwatt levels due to three-wave intermodulation to keep the signal-to-noise ratio from deteriorating significantly. As the number of channels increases, stimulated Raman scattering (SRS) begins to dominate. If a maximum of 0.5–dB depletion in the highest-frequency channel is allowed, SRS dominates when the number of multiplexed channels reaches about 300. Generally, the launch-power-limiting phenomenon is dependent on the number of channels being multiplexed.     

时间延迟积分型面阵CMOS图像传感器MTF速度失配模型研究

研究了时间延迟积分型面阵互补金属氧化物半导体(CMOS)图像传感器调制传递函数(MTF)速度失配特性,在分析累加级数、像素尺寸、镜头放大倍数、行周期及电机运动速度失配等影响因素的基础上,建立了MTF速度失配模型。基于现场可编程门阵列(FPGA)开发板,搭建面阵CMOS图像传感器实现线阵时间延时积分(TDI)的CMOS测试系统。实验结果表明,在光强为3lx,速度失配M(ΔV/V)<2,8级时间延迟积分与面阵成像相比,MTF值提高50%;当累加级数为8级,速度失配满足M(ΔV/V)=2的速度失配容限时,奈奎斯特频率处的MTF值下降10%,当速度失配达到M(ΔV/V)=10时,MTF值下降35%。     

The N-policy of a discrete time Geo/G/1 queue with disasters and its application to wireless sensor networks

We analyze an N-policy of a discrete time Geo/G/1 queue with disasters. We obtain the probability generating functions of the queue length, the sojourn time, and regeneration cycles such as the idle period and the busy period. We apply the queue to a power saving scheme in wireless sensor networks under unreliable network connections where data packets are lost by external attacks or shocks. We present various numerical experiments for application to power consumption control in wireless sensor networks. We investigate the characteristics of the optimal N-policy that minimizes power consumption and derive practical insights on the operation of the N-policy in wireless sensor networks.     

Lifetime maximization in wireless directional sensor network

This paper addresses two versions of a lifetime maximization problem for target coverage with wireless directional sensor networks. The sensors used in these networks have a maximum sensing range and a limited sensing angle. In the first problem version, predefined sensing directions are assumed to be given, whereas sensing directions can be freely devised in the second problem version. In that case, a polynomial-time algorithm is provided for building sensing directions that allow to maximize the network lifetime. A column generation algorithm is proposed for both problem versions, the subproblem being addressed with a hybrid approach based on a genetic algorithm, and an integer linear programming formulation. Numerical results show that addressing the second problem version allows for significant improvements in terms of network lifetime while the computational effort is comparable for both problem versions.     

物理实验中测温热电偶冷端补偿方法的改进

本文介绍了两种热电偶冷端温度补偿电路在物理实验测量中的应用及校准方法,对热电偶的工作原理、冷端温度补偿必要性作了说明,并详细介绍了冷端温度补偿过程．     

Novel coumarin-based containing denrons selective fluorescent chemosesor for sequential recognition of Cu2+ and PPi

In this study, we have successfully synthesized a novel coumarin-based dendrons derivative CD and its chemical structure was characterized by ¹H NMR, ¹³C NMR and ESI-HR-MS. The sensor CD showed an obvious “on-off” fluorescence quenching response toward Cu²⁺ with a maximum quenching efficiency of 99.8%. The CD-Cu²⁺ complex showed an “off-on” fluorescence enhancement response toward PPi over many competitive anions. The detection limit of the sensor CD was 0.29?×?10^?6?M to Cu²⁺ and 2.39?×?10^?9?M to PPi. In addition, the sensor CD showed a 1:1 binding stoichiometry to Cu²⁺ and the sensor CD-Cu²⁺ showed a 2:1 binding stoichiometry to PPi in CH₃CN/HEPES buffer medium (9:1 v/v, pH?=?7.2). The stable pH range of sensor CD to Cu²⁺ and CD-Cu²⁺ to PPi was from 3 to 8.     

A new “naked-eye” colorimetric and ratiometric fluorescent sensor for imaging Hg2+ in living cells

A new oligothiophene-based sensor 3 TH for monitoring Hg²⁺ has been designed and synthesized based on the intramolecular charge transfer (ICT) mechanism. The 3 TH shows the significant specificity toward Hg²⁺ through “naked-eye” colorimetric detection as well as via ratiometric fluorescence enhancement response with low detection limit of 62 nM. In addition, sensor 3 TH shows high selectivity and sensitivity for Hg²⁺ with fast response in a suitable pH range. Moreover, the 3 TH-based test strips was used to conveniently detect Hg²⁺ ions in water. Furthermore, considering its good ‘‘turn-on’’ fluorescent sensing behavior and low cell cytotoxicity, 3 TH was successfully applied to detect and image Hg²⁺ in real water samples and living cells, which shows great potentials for application in environmental and biological systems.