染料敏化太阳电池中TiO2膜内电子传输和背反应特性研究

采用强度调制光电流谱(IMPS)和强度调制光电压谱(IMVS)研究电池内部电子传输机理和电子背反应动力学特性.利用理论表达式对不同TiO2多孔膜厚度(d)的电池实验数据进行了拟合,得到了电池的吸收系数(a)、电子扩散系数(Dn)、电子寿命(τn)、电子传输时间(τd)和入射单色光光电转化效率(IPCE)等微观参数的数值.研究表明:膜薄有利于加快电子传输,膜厚有利于提高光生电子浓度,进而从微观层面上研究了薄膜厚度对于电池内部电子产生、传输和复合过程的影响.     

S—Ka频段电磁波在等离子体中传输特性的实验研究

在感应耦合等离子体风洞上开展了等离子体中电磁波传输特性实验研究,获得了不同频率电磁波在等离子体中的传输衰减.通过微波诊断技术,获得了等离子体射流的电子数密度和碰撞频率.通过矢量网络分析仪和标准增益天线组成的电磁波传输特性测试系统,获得了电磁波经过等离子体之后的衰减,研究了电子数密度范围7.0×10~(10)-1.0×10~(13)cm~(-3)、等离子体碰撞频率在109 Hz量级的等离子体对2.6—40 GHz不同频率电磁波传输特性的影响,分析了经典传输理论和薄层理论预测结果与实验结果的差异.该实验工作为等离子体中电磁波传输特性的理论研究和数值仿真提供了基础数据.     

基于太赫兹量子级联激光器的无线信号传输的实现

文章采用连续波激射的太赫兹量子级联激光器(THz QCL) 为发射端、光谱匹配的THz量子阱探测器(THz QWP) 为接收端, 搭建了基于THz波的无线传输演示系统. 测量并分析了该演示系统的传输带宽. 采用搭建的无线传输系统演示了基于4.13 THz电磁波的图片文件的无线传输过程, 得到了与源文件一致的结果, 验证了采用THz QCL和THz QWP进行THz信号无线传输的可行性.最后, 分析了演示系统的传输速率, 给出了提高系统传输速率的方法.     

自适应调制光正交频分复用系统的可变长保护间隔研究

利用保护间隔消除由色散引起的符号间干扰(ISI)对于光正交频分复用(OOFMD)系统是必不可少的.延时在不同的传输距离和传输环境下是不同的,采用固定保护长度的方式会硬响系统的功率和频谱利用率.提出了一种先进的自适应循环前缀(ACP)方法.对于多模光纤信道,循环前缀可以根据差分模延时(DMD)与传输距离确定其取值下限来消除ISI的影响.仿真实验验证,采取合适的保护间隔,在多模光纤传输10 Gb/s达1 km时,可达到与采用定长循环前缀时相同的传输性能.     

分布式EDFA中受激喇曼散射对光孤子脉冲传输的影响

本文用数值方法研究了透明传输下,受激喇曼散射(SRS)对由分布式掺饵光纤放大器(d-EDFA)级联的传输线中传输的光孤子脉冲的泵功率、孤子脉冲平均功率演化、均方根脉宽谱宽积、孤子系统的能量辐射、以及对光孤子传输稳定性的影响.结果表明:SRS降低了系功率,减弱了孤子平均功率起伏,有利于光孤子传输,但也使孤子脉(谱)宽展宽,增大了孤子系统的能量辐射,对孤子传输稳定性产生不良的影响.     

应用相敏光放大器的非零色散位移光纤通信系统中的ISI限制距离研究

本文分析了1.55μm信号波长,采用强度调制/直接检测(IM/DD)方式的单信道级联相敏光放大器(PSA)非零色散位移光纤传输系统的性能.应用非线性薛定谔方程(NLSE),通过对信号传输后眼图劣化度的计算,得到了光纤传输系统的码间干扰(ISI)限制距离.由于PSA的相敏特性,其对光纤色散具有一定的补偿作用,因此级联相敏光放大器光纤通信系统可以实现信号高比特率长距离传输.然而,随着信号速率的提高,对长距离传输,必须减小光纤色散值和PSA的间距.当光纤色散值大到一定程度,要进行信号的高速率传输,就必须附加其它的色散补偿方法.     

强散射过程中基于奇异值分解的光学传输矩阵优化方法

通过测量散射介质的传输矩阵能够控制光在此介质中的传输,但目前没有通过优化传输矩阵(即搜索介质本征传输矩阵)来提高光传输效率的研究.通过测量介质的传输矩阵进行奇异值分解与背景滤波,初步优化了传输矩阵后,提出通过遗传算法再次优化传输矩阵,实现了进一步优化传输矩阵,提高了聚焦效率和信噪比.所提方法为可见光在生物组织中的成像提供了一种新的思路和方法.     

染料敏化太阳电池中TiO2膜内电子传输和背反应特性研究

采用强度调制光电流谱(IMPS)和强度调制光电压谱(IMVS)研究电池内部电子传输机理和电子背反应动力学特性.利用理论表达式对不同TiO₂多孔膜厚度(d)的电池实验数据进行了拟合,得到了电池的吸收系数(α)、电子扩散系数(D_n)、电子寿命(τ_n)、电子传输时间(τ_d)和入射单色光光电转化效率(IPCE)等微观参数的数值.研究表明：膜薄有利于加快电子传 关键词： 染料敏化 太阳电池 IMPS/IMVS 传输     

添加势垒(阱)对光孤子在自聚焦克尔介质中传输的操控作用

为了操控在非线性克尔介质中传输的光孤子,以薛定谔方程为模型,采用分步傅里叶数值模拟的方法,分别研究了在非线性自聚焦克尔介质中添加高斯势垒、高斯势阱、Scarf-Ⅱ势垒(阱)和周期势垒(阱)后,光孤子在非线性克尔介质中的传输情况.通过改变势垒(阱)的高度(深度)、高斯势垒(阱)和Scarf-Ⅱ势垒(阱)的宽度,或者周期性势垒的周期,可实现对光孤子的操控.随着参数取值的不同,光孤子在传输中出现了反射、隧穿、周期性摆动、直线传播、分裂、光强增大等不同的现象.研究结果可为光开关和光控光技术提供参考.     

受激喇曼散射在掺铒光纤放大器中的影响

本文在分析了均匀掺杂分布式光纤放大器(d－EDFA)的基础上,提出了沿传输方向掺杂浓度单调下降(单变),和降升结合(两变)的两种渐变型分布式光纤放大器,并用传输方程研究了透明传输和最佳掺杂浓度下,受激喇曼散射对均匀、单变和两变型三种d－EDFA的各种特性的影响.     

Improved performance analysis of Gigabit passive optical networks

Gigabit passive optical networks (GPON) provide a capacity boosts in both the total bandwidth and bandwidth efficiency through the use of larger variable-length packets in Passive Optical Networks technology. In this paper, we have described a purely-passive GPON compatible reach extender using distributed Raman amplification and reported the improved investigation through implementation of a square root module by a distance of 60 km at data rate of 2.5 Gbps. An efficient improvement in Q factor is achieved with square root module, which further helps in increasing the length of GPON.     

Analysis of 2.5 Gbit/s GPON downlink optical-receiver performance

In the gigabit-capable passive optical network (GPON) optical communication system, the selection of fiber and system performance-analysis is the key links for the realization of system function. Especially the characteristic budget and parameter setting of downlink receiver are topped the list. The analysis of receiver power penalty can reduce the influence on receiver sensitivity and bit error rate (BER) that caused by waveguide dispersion and pulse widening. This article will simulate the performance of GPON downlink receiver, then analyze typical characteristics such as Four Wave Mixing (FWM), Erbium-Doped Fiber Amplifier (EDFA), system eye pattern and Q factor and so on, so as to validate the feasibility of the optical downlink.     

千兆无源光网络上行光信号特性研究与检测方案

由于千兆无源光网络系统中的上行光信号采用高速突发模式,故对其特性的检测是实现实时光层监测的难点.详细分析了上行光信号的传输特性、帧开销及噪声模型.并在此基础上,设计了一种检测方案,该方案通过高阻抗的前置放大器将信号引出,不影响原系统的正常工作,从而满足了实时检测的需要;通过峰值检波电路将高频突发信号降为低频进行处理,大...     

A novel algorithm to integrate synchronous digital hierarchy networks into Optical Transport Network using mixed line rates

In this era of high data transfer speeds and new age technologies, Optical Transport Network (OTN) along with its newly introduced Optical Transport Hierarchy (OTH) has provided a lease of life to legacy low rate networks. It has provided a common backbone for multiple data rates to coexist on same fiber along with the enhanced transmission reach. The cost effective Optical Transport Network design has always been a complex issue due to the presence of multiple variables like number of fibers on each link, available data rates on each fiber, the wavelength count, transmission reach at each data rate, etc. In this paper an Integer Linear Programming (ILP) model has been presented to solve Routing problem for Synchronous Digital Hierarchy (SDH) over OTN over DWDM design. Optical Transport Hierarchy (OTH) has been used to integrate heterogenous SDH/SONET operating at different rates (STM-16, STM-64 and STM-256) into a single network supporting mixed line rates. These rates can coexist in a same fiber but each rate carries different cost with it. The objective function aims at finding the least cost routing solution by looking at different tradeoffs between the Capital Expenditure and the operational expenditure. Certainly different variables like the number of fibers and wavelengths, transmission reach, etc. are a factor in it. A mechanism has been put to monitor the Bit Error Rate (BER) levels as well. For evaluating the ILP model, 18 Node 38 Link European Optical Network was considered as the reference model and two ordering techniques, namely, full ILP and highest rate first (HRF) were used for deriving the results. The ILP model was designed with minimum of decision variables so in spite of big reference network it converges much faster. Under the given conditions, full ILP gave least cost network whereas HRF ordering took least time for ILP to converge.     

基于SCFNN之PAM非线性信道均衡器成效研究

自组织型模糊类神经网络(SCFNN)可依据一定的法则自我构建神经网络的组织结构,从而适用于当前控制对象;多层神经元是传统的类神经网络,广泛应用于各个领域;倒传递学习法与最陡坡降法相结合,可使以上两种类神经网络进行有效的融合;目前,信道均衡器上的系统架构种类非常多,各种类神经网络应用于信道均衡器也颇为普遍;在研究SCFNN的基础上,将其应用于通道均衡器确实可行,效果良好;比较了SCFNN与MLP在通道均衡器的成效;仿真表明,在相同通道环境下,SCFNN的训练收敛速度、位错误率与系统敏感度优于MLP,完成结构学习后SCFNN的结构也颇为精简。     

Performance limits of pico-cell systems using radio-over-fiber techniques with an electroabsorption modulator

We investigate the performance limits of a pico-cell system using the radio- over-fiber technique with an electroabsorption modulator (EAM) in a 2.4 GHz wireless local area network (WLAN) environment. To understand the performance limits of the system using an EAM as the optical transceiver, we vary the optical modulation index (OMI) of the transmitter for different bias voltages to the EAM. Power margins in the links are found to estimate a possible service range, and packet loss rates (PLRs) in the pico-cell system are measured to evaluate the transmission performance. The total service range can be extended up to 3 m by adjusting the OMI of the transmitter for different applied bias voltages to the EAM.     

Application of phototransferred thermoluminescence (PTTL) for dose re-assessment in routine dosimetry using MTS-N (LiF:Mg,Ti) thermoluminescent detectors

Erasure of the thermoluminescence (TL) signal on detector readout is considered to be a disadvantage of TL dosimetry, as post-readout dose reassessment is then impossible in principle. A method of dose reassessment based on phototransferred thermoluminescence (PTTL) has been developed at the Institute of Nuclear Physics, Polish Academy of Sciences (IFJ PAN) and applied to MTS-N (LiF:Mg,Ti) detectors. We demonstrate the possibility of applying PTTL for dose reassessment in MTS-N TL detectors routinely applied in the dosimetric service at IFJ PAN. Readings of TL detectors exposed to relatively high doses by the customers of our dosimetry service can now be reassessed using our automatic readers. A major obstacle in applying the PTTL method at lower exposures is the presence of residual dose accumulated in LiF:Mg,Ti detectors after many field exposure and readout cycles. Since most of the TL detectors in our service have been already used for a long time (e.g. for over 10 years in the case of some detector batches), we find that our PTTL method of dose reassessment is possible only in detectors which had received doses exceeding 5 mSv.     

UWB LOS/NLOS identification in multiple indoor environments using deep learning methods

Indoor location-aware service is booming in daily life and business activities, making the demand for precise indoor positioning systems thrive. The identification between line-of-sight (LOS) and non-line-of-sight (NLOS) is critical for wireless indoor time-of-arrival-based localization methods. Ultra-Wide-Band (UWB) is considered low cost among the many wireless positioning systems. It can resolve multi-path and have high penetration ability. This contribution addresses UWB NLOS/LOS identification problem in multiple environments. We propose a LOS/NLOS identification method using Convolutional Neural Network parallel with Gate Recurrent Unit, named Indoor NLOS/LOS identification Neural Network. The Convolutional Neural Network extracts spatial features of UWB channel impulse response data. While the Gate Recurrent Unit is an effective approach for designing deep recurrent neural networks which can extract temporal features. By integrating squeeze-and-extraction blocks into these architectures we can assign weights on channel-wise features. We simulated UWB channel impulse response signals in residential, office, and industrial scenarios based on the IEEE 802.15.4a channel model report. The presented network was tested in simulation scenarios and an open-source real-time measured dataset. Our method can solve NLOS identification problems for multiple indoor environments. Thus more versatile compare with networks only working in one scenario. Popular machine learning methods and deep learning methods are compared against our method. The test results show that the proposed network outperforms benchmark methods in simulation datasets and real-time measured datasets.     

Performance investigation on harmonic distortion and inter-modulation distortion induced degradation for a single- and two-tone IM-DD SCM optical link

Subcarrier multiplexing (SCM) has been utilized for data transmission in high performance broadband in access networks which requires high transport capacity and throughput with guaranteed quality of service. In a transmitter employing SCM technique in an Intensity Modulation Direct Detection (IM-DD) system, laser source nonlinearity is an important issue of concern. This work investigates the sensitivity of resulting harmonic distortion (HD) and inter-modulation distortion (IMD) to changes in subcarrier amplitude, laser bias current operational parameters and laser quantum efficiency, laser active layer volume and laser carrier life time design parameters. Results show that IMD impairment mechanism is more dominant than HD mechanism. The spectrum analyser shows distinct difference in the frequency domain display of HD and IMD dominated systems. HD and IMD mechanisms show high sensitivity to carrier amplitude and active layer volume with a positively increasing slope gradient and high sensitivity to bias current and carrier life time with negatively decreasing slope gradients. Also these impairments are moderately sensitive to laser quantum efficiency. The investigations will help in identification of the most influencing operational and design parameters and their suitable values to be used to effectively reduce the influence of the source nonlinearity of SCM links.     

Virtualized Networks and Virtualized Optical Line Terminal (vOLT)

The success of the Internet and the proliferation of the Internet of Things (IoT) devices is forcing telecommunications carriers to re-architecture a central office as a datacenter (CORD) so as to bring the datacenter economics and cloud agility to a central office (CO). The Open Network Operating System (ONOS) is the first open-source software-defined network (SDN) operating system which is capable of managing and controlling network, computing, and storage resources to support CORD infrastructure and network virtualization. The virtualized Optical Line Termination (vOLT) is one of the key components in such virtualized networks.