Monitoring shear deformation of sliding zone via fiber Bragg grating and particle image velocimetry

Monitoring shear deformation of sliding zones is of great significance for understanding the landslide evolution mechanism,in which fiber optic strain sensing has shown great potential.However,the cor-relation between strain measurements of quasi-distributed fiber Bragg grating(FBG)sensing arrays and shear displacements of surrounding soil remains elusive.In this study,a direct shear model test was conducted to simulate the shear deformation of sliding zones,in which the soil internal deformation was captured using FBG strain sensors and the soil surface deformation was measured by particle image velocimetry(PIV).The test results show that there were two main slip surfaces and two secondary ones,developing a spindle-shaped shear band in the soil.The formation of the shear band was successfully captured by FBG sensors.A sinusoidal model was proposed to describe the fiber optic cable deformation behavior.On this basis,the shear displacements and shear band widths were calculated by using strain measurements.This work provides important insight into the deduction of soil shear deformation using soil-embedded FBG strain sensors.

Hygrothermal/UV Aging Effect on Visual Aspect and Mechanical Properties of Non-Woven Natural-Fiber Composites

This work aims at studying the effect of hygrothermal and UV cyclic aging on the tensile properties and esthetic characteristics of non-woven composites.The composite materials were thermo-compressed from non-woven mats made up of PP and flax or kenaf fibers.This works included evaluating the change in color appearance and analyzing the variations in tensile properties and damage mechanisms,depending on the aging time.The presence of the UV protection film on the composite surface showed its effectiveness against aging.From visual observations and measurement of colorimetric parameters,it has been proved effective in the reduction of the bleaching and yellowing of the composites.As regards the tensile tests,the UV protection film enabled to stabilize the Young’s modulus after 1-week aging for Kenaf/PP and after 3-weeks for Flax/PP.After 4-weeks aging,it halved the number of acoustic emission events related to interfacial decohesion and fiber slippage/pull out for Flax/PP and Kenaf/PP composites.

Experimental Observation of Dark Soliton Emitting with Spectral Sideband in an All-Fiber Ring Cavity Laser

The dark soliton pulse with spectral sideband is experimentally observed in a dispersion-managed ail-fiber ring laser with net negative cavity group velocity dispersion.We find that,for single or multiple dark solitons,the spectral sidebands always appear and exhibit asymmetric characteristics which are similar to bright solitons.The experimental measurements of spectral sideband positions are carried out and the results are in good agreement with the calculated values.Our results show that spectral sideband effect is also an intrinsic feature of a dark soliton fiber laser.

基于Super C Band的可调增益掺铒光纤放大器设计

随着网络业务流量的增长,通信业务对密集波分复用(DWDM)的性能要求越来越高。为了提高传输效率,传输频谱逐渐向C+L Band传输扩展,Super C Band传输应运而生,但目前与之对应的掺铒光纤放大器(EDFA)相关研究较少。针对这一问题,文章提出了一种针对Super C Band传输的EDFA结构,基于Giles模型,分析了EDFA在Super C Band的特性,利用多级泵浦机制,设计了一种可以在Super C Band范围内进行放大的EDFA。结果表明,在-9.3 dBm入光时,该EDFA可以实现26 dB的平坦增益,16.7 dBm的输出功率,此时噪声指数小于5 dB,Ripple小于0.1 dB。并且根据需要,在入光处于-15.0~-3.5 dBm范围内时,通过调节泵浦功率与可调衰减器,均能够实现7~26 dB的可调增益。该EDFA可应用于5G传输和数据中心之间光纤通信等场合。

High Oil-absorptive Composites Prepared from Non-woven Fiber and Sponges with 4-tert- butylstyrene-EPDM-divinylbenzene Graft Polymer

4-tert-butylstyrene-EPDM-divinylbenzene graft terpolymer (PBED) was prepared by graft cross-polymerization in toluene using BPO as an initiator. The gel-PBED and solPBED were isolated from extraction of tetrahydrofuran (THF), and then they were identified by IR spectroscopy. The maximum oil-absorptivity of gel-PBED produced from the optinum reaction conditions was 8 420% but its swelling rate was very low. The highest oil-absorptivity of photocrosslinked sol-PBED film was 5 800%. Although its oil absorbency was not as high as gel-PBED' s, swelling rate was higher than that of gelPBED and was suitable for commercial purpose. After swelling in oil, neither gel PBED nor photocrosslinked sol-PBED film having high oil-absorptivity had sufficient mechanical strength to be taken out of oil wholly. As is known, composite technique is one of the useful methods for reinforcing them. Fibers, sponges and non-woven cloths were used as reinforcers or supporters in this work. Oil-absorptivities and swelling kinetics were evaluated by method ASTM (F726 - 81 ) and an experimental equation. The mechanical properties and the morphologies of some composites were measured by tensile tester and SEM , respectively.

Radio over Fiber Architecture Very High-Speed Wireless Communications in the Unlicensed 60 GHz Band

Larger wireless access networks are required to meet the growing demand for mobile traffic and multimedia services. The use of RoF (Radio over Fiber) technology in combination with millimeter waves is a potential response to the requirements of broadband applications and high capacity networks. In this paper, we proposed a RoF architecture able to provide very high-speed wireless access points up to Gbps considering an indoor and outdoor environment conform to IEEE 802.11ad and IEEE 802.15.3c standard. Optical transmission and radio coverage have been studied by considering the uplink and downlink. System performance has been evaluated in the relation to the Error Vector Magnitude (EVM) for various modulation formats (BPSK, QPSK and 16QAM). Results showed that millimeter wave signals are successfully delivered over a 50 km fiber link and a wireless channel up to 32 m. Data throughput up to 5.28 Gbps has been reached. The proposed architecture can extend the range of applications for wireless communications in association with the unlicensed 60 GHz band with the advantages of better capacity, a wider coverage area and a reduction in the investment cost.

Fabrication and Optical Characterization of Palm Fiber Reinforced Acrylonitrile Butadiene Styrene Based Composites: Band Gap Studies

The composite materials are replacing the conventional materials, owing to their excellent properties. The developments of new materials are on the anvil and are thriving day by day. Natural fiber composites such as palm fiber (PF) polymer composites became more enchanting because of their high specific strength, low weight and biodegradability. Mixing of natural fiber like PF with acrylonitrile butadiene styrene (ABS) polymer is finding increased applications. In this work, PF reinforced ABS composites PF-ABS was fabricated by Injection Moulding Machine. The effect of UV-Visible radiation on PF-ABS composites was studied by means of ultraviolet-visible spectroscopy in the wavelength 200 - 1000 nm at room temperature. The present investigation shows that the addition of palm fiber modifies the absorption property of the materials. The absorption ability is maximal for 10% PF-ABS composites while minimal for 20% PF-ABS composites in the visible region of the spectrum. Optical constant like direct band gap energy, Urbach energy and Steepness parameter were determined using absorbance data. The values of direct energy band gap, Urbach energy as well as Steepness parameter were found to be in the range 2.6 - 3.9 eV, 0.40 - 0.85 eV and 0.03 - 0.06, respectively. It was observed that the value of direct band gap energy as well as Urbach energy is higher while the value of Steepness parameter is lower for PF-ABS composites with 10% palm fiber.

A novel 3-stage structure for a low-noise, high-gain and gain-flattened L-band erbium doped fiber amplifier

The configuration of the novel three-stage L-band erbium-doped fiber amplifier with very large and flat gain and very low noise figure presented in this paper uses the forward ASE (amplified spontaneous emission) from the first section of the EDF (erbium-doped fiber) and the backward ASE from the third section of the EDF (both serve as the secondary pump sources of energy) to pump the second EDF. To improve the pump efficiency, the power of the pump is split into two parts (with a ratio of e.g. 2:7). The characteristics of this L-band EDFA are studied on the basis of the Giles Model with ASE.

Design and Modeling of S Band Circular Patch and Ka Band Horn Antenna, Integration with Future Multifunctional Radio over Fiber Network

Radio over Fiber is an integration of microwave and optical fiber technologies having numerous benefits. RoF technology can give a scope of advantages including the capacity for backing multiple radio services and standards. In coming future, there is need of integrated wireless service with high speed satellite broadband and multifunctional indoor/outdoor antennas. Radio over fiber is one of the most favorite candidates to meet all these requirements of future multifunctional integrated wireless communication. Due to planer profile, small size and low cost patch antennas are most favorite to use for multi- frequency applications. In this paper, we present system level design for future multifunctional radio over fiber network. Under FTTH (Fiber To The Home) technology, it will be possible to use multi-frequency applications on single fiber medium. Firstly, we designed S band circular patch antenna (2.5 GHz) and Ka band (29 GHz) horn antenna. Circular patch antenna performance is estimated with different substrate height. After getting S parameters and far-field results, we did modeling of Radio over Fiber system over (10 Km) with same parameters from antenna results.

由Giles模型对L-band EDFA的理论分析

本文通过运用Giles模型对L bandEDFA在不同泵浦波长下的增益、不同泵浦功率与光纤长度的关系以及各种增益特性等进行了数值模拟 ,并同时辅以C bandEDFA进行比较计算 ,从理论上对L bandEDFA的特性进行了较为详细的分析说明 。

L-Band掺铒光纤放大器的优化设计

提出了泵浦分配两段级联 ,并利用前向ASE推动下一级EDF工作的L Band放大器的新结构 基于Giles模型并考虑了ASE噪声的影响 ,运用数值模拟算法系统分析了泵浦光功率分配和铒光纤分配比例对这种EDFA性能的影响 最后优化得到高增益且增益谱平坦的L BandEDFA ,其在输入信号光功率为 - 2 0dBm时 ,在 15 71～ 16 0 8nm范围内 ,增益值高达 35dB ,增益偏差小于

基于色散调控氟碲酸盐玻璃光纤的O-U波段平坦光频梳产生

光学频率梳(简称光频梳)作为一种优秀的多波长光源在通信领域具有巨大的应用潜力。通过将光频梳光源与波分复用技术(WDM)、空分复用技术结合(SDM),通信系统可以具有百Tbit/s量级的传输速率,在5G/6G通信、物联网、自动驾驶等方面具有重要的应用价值。目前实现光频梳的方法主要有以下四种,分别为基于锁模激光器产生飞秒光频梳、基于光学微腔产生光频梳、基于电光调制器产生光频梳以及基于行波四波混频产生光频梳。它们各具特点,但均很难同时实现宽光谱、高信噪比、高平坦度、高的单梳齿功率以及梳齿频率间隔大范围可调,这在一定程度上影响了光频梳在光通信领域的应用。本文提出基于受激布里渊激光腔产生种子梳,采用腔外负色散光纤进行脉冲压缩,进一步利用色散调控的高非线性氟碲酸盐光纤进行扩谱,从而实现光频梳产生。数值计算结果表明,通过该系统,我们可以得到重复频率大范围可调、光谱覆盖整个O-U波段且在O-U波段梳齿强度标准差小于5 dB的平坦光频梳,证明了通过基于布里渊激光腔与色散调控高非线性氟碲酸盐光纤的光学系统产生可用于光通信的平坦光频梳的可行性。

利用电光FM调制抑制零级中心频带——实现超高频Radio over Fiber通信

提出了一种有效抑制零级中心频带方案,并证实了该方案的可行性,给出了基于该方案的单工Radioover Fiber(RoF)通信系统.通过光通信系统软件Optisystem5.0仿真模拟结果显示:光源发送功率为5dBm,途中无光放大,24GHz的超高频微波信号在色散系数为20ps/nm/km、衰减系数为0.25dB/km的单模光纤中传输,系统码元传输速率可达5Gbit/s、传输距离15km以上.

基于外部气相沉积的S+C+L波段低色散斜率大有效面积非零色散位移光纤的设计与制备

针对现有光纤无法满足宽带光密集波分复用系统传输和S+C+L波段粗波分复用的要求,设计了一种具有中心凹陷的三角形芯+环形的折射率剖面,利用外部气相沉积工艺制备了一种非零色散位移光纤,并通过调整第一芯层的相对折射率和第二芯层与第一芯层的半径比,探究了其对光纤衰减、色散斜率和有效面积等参数的影响。研究发现,当第一芯层的相对折射率逐渐增大且第二芯层与第一芯层半径比逐渐减小时,零色散波长和有效面积逐渐减小。当第一芯层的相对折射率在0.52%~0.53%,芯层半径比在2.6~2.7时,光纤的有效面积接近70μm^(2),零色散波长在1420 nm附近,在1550 nm波段的色散系数大于8 ps·nm^(-1)·km^(-1),色散斜率为0.059 ps·nm^(-2)·km^(-1),可以较好地抑制传输过程中光非线性效应,满足长途干线网与城域网的使用要求。

L-band增益平坦EDFA的研究

使用数值计算方法对L-band EDFA小信号增益特性和L-band EDFA中各种光束随EDF长度的变化进行了模拟,得到了L-band EDFA增益具有本征平坦特性的结论,并为L-band EDFA低泵浦转换效率提供了合理解释。在数值模拟的基础上,进行了增益平坦L-band EDFA的实验,获得L-band30nm波长范围内增益变化不超过0.5dB平坦增益的实验结果,并借助FBG有效地提高了泵浦转换效率。

低损耗紫外空芯反谐振光纤的设计与研究

通过仿真模拟设计了一种低损耗紫外空芯反谐振光纤。首先,基于有限元法,建立了紫外空芯反谐振光纤的理论模型。其次,通过调整光纤反射层和空气填充比例等参数,并采用反谐振效应控制光的传播和反射,进一步优化了光纤的性能和损耗值。最后,采用有限元法对设计的紫外空芯反谐振光纤进行仿真计算,可得光纤在传输波长为375nm时取得最小传输损耗,为0.00326dB/m,对应的在弯曲半径为5cm时的弯曲损耗为0.00625dB/m,并具有高效率和稳定的模式输出。该研究为开展紫外空芯反谐振光纤的高性能仿真设计提供了重要的参考和指导,并为实际应用提供了更多可能性。

L-band可调谐掺铒光纤环形激光器的研究

提出一种新颖高效的L带波长可调谐掺铒光纤激光器,激光器采用环形结构,腔内利用两段掺铒光纤和一个光线光栅以提高泵浦效率。同时应用了基于光纤环形镜的可调谐滤波器作为腔内波长选择器和线宽压缩器。实验获得的激光输出可调谐范围达42 nm,输出功率超过1 mW,功率均匀度控制在1.75 dB以内,边模抑制比大于40 dB。

增益光纤类型与L-band EDFA的性能关系

为分析增益光纤对L波段(L-band)掺铒光纤放大器(EDFA)增益特性的影响,基于G iles模型对不同增益光纤构成的EDFA进行了数值模拟和实验研究,模拟和实验表明,L-band EDFA增益值的大小与EDF掺杂浓度、泵浦功率及光纤长度有关,光纤长度越长,则达到平坦增益时需要的泵浦功率就越大,本征平坦增益值也越高。

低噪声、高增益的L-band EDFA的实验研究

针对传统的LbandEDFA的工作效率低,提出了一种基于单根光纤光栅、泵浦分配、两段级联的EDFA的新结构,其中的光纤光栅用来反射无用的后向CbandASE系统地研究了泵浦比例和光纤光栅波长对增益噪声指数的影响关系最后经实验验证,得到了低噪声、高增益的Lband的EDFA其在输入信号光(1570nm)功率为-30dBm及泵浦功率为70mW时,增益为22.26dB,增益噪声指数为4.

泵浦源对L-band EDFA增益特性的影响

对不同泵浦波长的L-波段(L-band)掺铒光纤放大器(EDFA)的增益特性进行了研究,模拟和实验表明:L-band EDFA本征平坦增益值的大小与EDF长度有关,与选择的泵浦波长无关,但泵浦效率受泵浦波长影响很大,泵浦波长越长,则泵浦转换效率越高。