最新刊期
卷 ， 期 3 ， 2016
- 摘要：Subcarrier allocation is one of the key technologies in the Orthogonal Frequency Division Multiplexing Passive Optical Network（OFDM-PON）,which has been received more and more attentions recently.This paper first introduces two existing subcarrier allocation schemes.Then a novel subcarrier allocation scheme is proposed for upstream transmission in OFDM-PON.The scheme is divided into two parts:modulus operation and patchwork scheme.The scheme can effectively reduce the waste of bandwidth of guard time.Simulation results show that the proposed scheme obtains higher throughput compared to existing schemes.关键词：OFDM-PON;subcarrier allocation;throughput
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发布时间： - 摘要：In order to solve the inefficient spectrum utilization problem in fixed-grid WDM networks,an upgrading scheme is proposed to upgrade the bottleneck links from fixed grid to flex grid networks.The paper defines the concept of bottleneck links,and proposes two strategies:the Link Density（LD）strategy and the congestion strategy.Numerical results show that the Bandwidth Blocking Rate（BBR）is reduced by the two strategies.The LD strategy performs different BBR reduction depending on different thresholds and the congestion strategy can effectively reduce the BBR.关键词：WDM networks;flex grid;bottleneck link;BBR
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发布时间： - 摘要：Targeting on the link optimization configuration problem for high-speed coherent optical transmission systems,a successive optimization principle based link EDFA gain configuration scheme is proposedto optimize the system performance improvement and tuning cost in irregular link configurations.The optimization object is to reduce the number of adjusted EDFAs in the transmission link when the optimal performance is achieved.Such scheme aims to reduce or even avoid the delay,transient and costs induced by the link power adjustment.The simulation results show that the proposed scheme can reduce the number of adjusted EDFAs from 8 to 4,when the system performance is still close to the optimum value.Thus this scheme effectively reduces the tuning cost caused by frequently adjusting the EDFA gain in the optimal configuration scheme.关键词：coherent optical transmission;Transmission performance optimization;link adjustment
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发布时间： - 摘要：To meet the growing demand of the further application of distribution automation,data services and network bandwidth,the scheme which combines the Time Division Multiplexing（TDM）and packet transmission technology is proposed in this paper.The scheme is based on an integrated service delivery isolation algorithm.The effectiveness of the algorithm is verified by the use of Ethernet switches and integrated optoelectronic devices,which compare the degree of isolation for the respective transmission services.The results show that the proposed algorithm can achieve high efficiency utilization for the power transmission resources.关键词：optoelectronic integration;isolation degree;frequency entropy
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发布时间： - 摘要：An integrated security scheme for 10Gbit/s EPON is proposed to prevent eavesdropping and masquerading threats to sensitive data caused by its point-to-multi-point topology.This scheme includes a bilateral authentication method combining with key exchange protocol and an encryption algorithm based on the timestamp.The authentication method can verify the OLT and ONU during the registration process and the encryption algorithm adopts timestamp in the frameto generate time-varying cipher keys.The validity of the proposed scheme is demonstrated in the experiment.关键词：10Gbit/s EPON;bilateral authentication;encryption algorithm;security
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发布时间： - 摘要：At present,passive maintenance of elements and alarms trigged in the Optical Transport Network（OTN）can not meet the requirements of complex network management.In this paper,we propose the graded early-warning algorithm before the fault occurred by sorting out various types of important service-related alarm titles and analyzing the related effects in the OTN management system.The proposed method provides an effective statistical model for early-warning alarm and rapid response scheduling in the OTN.关键词：optical transport network;graded;alarm
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发布时间： - 摘要：Phase noise is one of the key limitations for phase-modulated signal in high-speed optical communication system as its information is coded in the optical phase.Therefore,phase noise monitoring technique is highly required in future reconfigurable and flexible optical communication system.It can provide real-time information about the quality of the transmitted signal during the fiber transmission.In this paper,we apply the phase sensitive characteristic in the parametric amplifying process and propose a phase noise monitoring method for Binary Phase Shift Keying（BPSK）signal based on dual-pump parametric amplifying in highly nonlinear fiber.The simulation results show that the phase noise monitoring can be successfully achieved in the range of 0 to 0.4 Vπ for 40Gbit/s BPSK signal.关键词：optical communication;BPSK;phase noise;parametric amplifying
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发布时间： - 摘要：Coverage holes phenomena is appeared in the process of random deployment of wireless sensor network systems.This paper presents a probabilistic model by means of event-driven policy coverage holes compensation method（Coverage Holes Compensation Algorithms Based on Event-Driven Strategy,CHCAEDS）.Firstly,the characteristics of random deployment are verified and the representation of random deployment is given.Then,based on the probabilistic method,the desired coverage and the number of nodes within the surveillance area are solved in order to achieve maximum coverage area using minimum number of nodes.Finally,the simulation result show that the CHCAEDS can improvethe network life cycle and the algorithm running time by 12.59% and 10.82% when comparing with other algorithms.关键词：wireless sensor networks;coverage quality;coverage holes;event-driven strategy
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发布时间： - 摘要：A new Photonic Crystal Fiber（PCF）with flattened chromatic dispersion and low confinement losses is proposed by varying the size of air hole.By employing a Full Vector Finite-Element Method（FVFEM）and Anisotropic Perfectly Matched Layers（APML）,the structure and optical properties of the proposed PCF are analyzed.The simulation is conducted under the conditions that the effective refractive index of air hole at 1.55μm is n0 =1 and the effective refractive index of quartz is 1.45.The results show that the proposed PCF has ultra-flattened dispersion of 0±0.68ps/（nm·km）from 1.25μm to 1.78μm wavelength range with confinement losses lower than 10-3 dB/m across all the wavelength range.关键词：PCF;dispersion;confinement losses;elliptical hole
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发布时间： - 摘要：Three-core optical fiber composite submarine power cable is often stretched in the process of transportation,installation and operation.The stress and strain data can be obtained by the simulation of stretching modeling,which is difficult to be obtained in the entity experiment.In this paper,the finite element model of the submarine cable is established,which is used to simulate the stretching process.We first simplify the structure of the submarine power cable according to the mechanical characteristics of stretching.The constraint,speed loads and hourglass control are then imposed to simulate the axial stretching process.Finally,the stress and strain data of the finite element model is extracted and processed to obtain the stress and strain of the submarine cable.The results provide reference for the study of mechanical properties and operating condition judgement of the submarine power cable.关键词：three-core optical fiber composite submarine cable;stretch;stress;strain;finite element
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发布时间： - 摘要：In the process of loading transportation,installation and operation,the submarine cable is usually suffered from twist problem due to many external factors.The method of modeling and simulation can not only overcome the difficult problems in the entity experimental operation,but also obtain the stress and strain which is difficult to obtain in the entity experiment.In this paper,the finite element model of submarine cable torsion is first built.Then we select the unit type,material properties and parameters of each layer.Next,we analyze the factors that will influence the computation time and simulation precision.Finally,the constraint and speed loads are imposed to the model,which simulate the stretching twist process to obtain the stress and strain data.The modeling method in this paper provides a feasible solution to analyze the mechanical characteristics of submarine cable twist.关键词：optical fiber composite submarine power cable;twist;stress;strain;finite element analysis
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发布时间： - 摘要：Analyzing from the data of historical temperature to decide the situation of bugs or aging of submarine cable is a critical issue in practical situation.To solve these problems,Empirical Mode Decomposition（EMD）is used toextract the time-frequency characteristics of historical temperature of the submarine cable.Then,the similarity of the frequency characteristics of the submarine cable is examined via matrix calculation at different positions.Finally,the position of the problematical marine cable will be located through the analysis of the abnormality of the similarity.The experimental result shows that the similarities between the positions of problematical submarine cable are bounded to less than the regular one.Therefore,the position of the problematical marine cable can be accurately located.关键词：EMD;matrix similarity;time-frequency characteristics
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发布时间： - 摘要：A C6v TIR-PCF（the six-fold rotation symmetry total internal reflection photonic crystal fiber）of cladding with hexagonal air column is designed in this paper.The fundamental mode dispersion characteristics are investigated numerically by full vector finite element method.The numerical results show that when other parameters are unchanged,original two fundamental mode polarization are separated if the shape of the cladding air column changes from circular to hexagonal.We can also observe a large mode birefringence and high degree of polarization mode dispersion.The results also show that the wavelength dispersion of the fundamental mode in Xpolarization have the same variation curve with cladding circular air column.It means that the fundamental mode dispersion characteristic has a great influence on the shape of cladding air column.关键词：C6v total internal reflection photonic crystal fibers;full vector finite element method;the fundamental mode dispersion characteristics
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发布时间： - 摘要：The method of the optical cable usability evaluation is proposed based on the performance indicators forecast in order to accurately assess whether the existing optical cable can be adapted to the high-performance optical equipment in the future.A model which can accurately predict the performance of the optical cable is first built.Then the method predicts the usability of the optical cable according to the requirements of the allowable loss range of the optical equipment based on the model.The accuracy and validity of the method is demonstrated via the experiment.The proposed method may provide reference and guidance to solve the problem of cable usability evaluation.关键词：usability evaluation;transmission performance index;combination model;forecasting
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发布时间： - 摘要：In this paper,we investigate the method to improve the thermo-optic modulation efficiency of Waveguide Bragg Gratings（WBG）based on polymer material.According to the optical characteristics of polymer materials,a third-order WBG is designed.The effects of WBG structure parameters on the optical transmission spectrum of the WBG are also analyzed. In order to improve the thermooptic modulation efficiency,anembedded electrode structure combined with the Air Trenches（AT）symmetrically beside the WBG is proposed. The simulation results show that the wavelength-tuning sensitivity of the propose WBG structureis increased by 1. 87 times,which can achieve a broad wavelength-tuning range. Compared with general thermo-optic modulation structures,the designed thermooptically tunable WBG features strong heated ability,high heat uniformity and low thermal crosstalk.关键词：waveguide Bragg grating;polymer;thermo-optic effect
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发布时间： - 摘要：In non-conventional oil and gas exploitation field,micro-seismic monitoring technology requireshigh resonant frequency micro-seismic sensor. In this paper,a Fiber Bragg Grating（FBG）micro-seismic geophone with high resonant frequency based on elastic light-walls tube is proposed. The mechanical model,the amplitude-frequency and the sensitivity of the geophone are theoretically analyzed and experimentally measured. Experimental results show that the resonant frequency is 1 680 Hz.In the operating range of 50 1200 Hz,the linear fitting degree is 0.998 4 and the acceleration sensitivity is 4.393 2 pm / G. The relative error is 0.15% between the experimental result and theoretical analysis.关键词：fiber optics;FBG;micro-seismic sensor;sensitivity
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发布时间： - 摘要：According to the rigorous coupled-wave theory and medium slab waveguide theory,the structure of Distributed Feed Back（DFB）semiconductor laser based on single-crystal n-ZnO/p-AlGaN Light Emitting Diode（LED）structure is simulated and designed by the Comsol Multiphysic software. The distribution of a two-dimensional electric mode is analyzed with near-ultraviolet light emission at the applied voltage of 4 V on the n-ZnO / p-AlGaN LED structure. The variation of the single longitudinal mode with different parameters of the grating is obtained. Also,the simulation results show that the electric field mode reached 5. 877 4 × 107 V / m with narrow spectral linewidth and preferable mode selectivity under the condition of the duty ratio of 50%,grating period of 109.2 nm and the grating height of 69.8 nm. The results in the paper provide a foundation for the design and processing of electrically pumped DFB semiconductor laser.关键词：LED structure;DFB semiconductor laser;ZnO;electrically pump
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发布时间： - 摘要：The application of Surface Plasmon Polariton（SPP）suffers from high loss during propagation and contradiction between subwavelength constraints and propagation distance. The paper proposes an asymmetric dielectric waveguide structure and designsa loaded glass SPP propagate optimization device.The excited model of SPP is similar to Kretschmann structure. It can improve the propagation distance without sacrificing the size of subwavelength waveguide. The Finite Difference Time Domain（FDTD）analysis results show that the improved waveguide structure can significantly increase the SPP propagation distance with higher electric field strength. The SPP propagation distance is increased by more than 20 times. We also compare the performances with different thickness of film layers.The result indicates that the better localization performance can be achieved with thinner film. The proposed structure also significantly increases the SPP coupling effect. The proposed structure has the potential for the application of SPP in the area of new photonic devices,broadband communications systems,small photon loops,and other aspects of integrated optoelectronic applications.关键词：subwavelength optics;Insulator-Metal-Insulator（IMI）waveguides;loads of glass;Kretschmann structure
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发布时间： - 摘要：A novel Optical Orthogonal Frequency-Division Multiplexing（O-OFDM）scheme is proposed for Intensity-Modulated Direct-Detection（IM/DD）systems named Hartley Polar O-OFDM（HP-OFDM）.A large amount of operation time and memory can be saved for the system based on Fast Hartley Transform（FHT）when compared with conventional Cooley-Tukey Fast Fourier Transform（FFT）,which is especially suitable for hardware implementation.It is also noted that the unipolar process of OFDM can be performed in polar coordinate.The simulation results show that the HP-OFDM can provide better BER and Peak-to-Average Power Ratio（PAPR）performances than ACO-OFDM under the same spectral efficiency condition.关键词：O-OFDM;Hartley transform;BER performance;PAPR;spectral efficiency
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发布时间： - 摘要：The communication rate and reliability is greatly affected by the channel fading effect.In order to solve the problem,we propose a method based on Signal Space Diversity（SSD）in OFDM modulation scheme in this paper.The experimental results show that the method can achieve 0.71.3dB Bit Error Rate（BER）improvement at the data rate of 120160Mbit/s in fading environment with over 924dB attenuation in Visible Light Communication（VLC）system.关键词：indoor white LED;VLC;SSD;OFDM
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发布时间： - 摘要：In order to reduce the bit error rate and improve the transmission performance of the Visible Light Communication（VLC）system,the channel equalization technology is studied in this paper. The channel model of the indoor VLC system is established. The direct impulse response and reflected impulse response of the channel are also analyzed. A new variable-step-size Least Mean Square（LMS）algorithm is used to compensate the Inter-Symbol Interference（ISI）induced by multi-path effects. The experimental results show that the proposed LMS algorithm has faster convergence rate,which can achieve lower bit error rate when the system is stabilized.The adaptive equalizer has a better tracking performance on time-varying channel and system steady-state error is also reduced.关键词：VLC;LMS algorithm;ISI;adaptive equalization
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发布时间： - 摘要：The fast development of communication technology and the increasing demand of the users result in the phenomenon that the load in the cell becomes more and more unbalanced.In this paper,we propose an algorithm based on load pre-allocation for Long Term Evolution（LTE）network to solve the problem.When a cell becomes overload,we select the optimal target cell through analytic hierarchy process method,which can reduce the ping-pong handover rate.Then we allocate the load in the overload cell according to the measurement of the load in the target cell.Finally,we adjust the cell individual offset to transfer the users to realize the inter cell load balancing.The simulation results show that the proposed algorithm can effectively improve the inter cell load balancing degree and the users’ experiences with smaller handover numbers.关键词：LTE;mobility load balancing;analytic hierarchy process;cell individual offset
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发布时间： - 摘要：To solve the problems of the channel blur,limited channel capacity and higher error rate in Multiple-Input Multiple-Output（MIMO）system,we propose a new channel equalization method to compensate the channel distortion to increase the anti-interference,and enhance the reliability and stability of the transmission system. The method is based on the combination of Constant Modulus Algorithm（CMA）and adaptive beamforming technology in MIMO system with Quadrature Phase Shift Keying（QPSK）modulation. The experimental results show that the proposed QPSK equalization technique can solve the contradictory problem between channel capacity and the bit error rate,and reduce the inter-symbol interference and channel interference. In addition,it can achieve the best performances by correcting the phase error with faster the convergence speed and lower bit error rate lower.关键词：MIMO system;QPSK modulation;CMA;adaptive beamforming
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发布时间： - 摘要：Distribution Automation（DA）technology is a key technology in the DA management system.This paper discusses the pros and cons of different communication techniques（i.e.,optical fiber communication,power line communication and broadband wireless communication）in DA.Based on the comparison,we further discuss the wireless broadband technique based on Long Term Evolution（LTE）.Finally,we build the simulation platform and simulate two typical scenarios in the application of smart metering（i.e.,periodic reporting and power recovery）.We evaluate the performance of LTE for the business of DA with both FDD and TDD modes.The results show that both the two modes can meet the requirement of Quality of Service（QoS）for the business of periodic reporting resident power consumption.Particularly,LTE-FDD system is more suitable for this business.In the scenario of power recovery after power outage in the residential areas,further optimizations at the wireless side are required for both LTE-TDD and LTE-FDD systems to solve the congestion problem caused by massive simultaneous access of smart metering terminal.关键词：DA;broadband wireless network;FDD-LTE;TDD-LTE
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发布时间： - 摘要：<正>科技论文的引言是简要说明研究的主要目的、范围,即为什么写这篇论文以及要解决什么问题;前人在本课题相关领域内所做的工作和尚存的知识空白,作简要的历史回顾和现在国内外情况的横向比较;研究的理论基础、技术路线、实验方法和手段,以及选择特定意见方法的理
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