最新刊期
卷 ， 期 1 ， 2015
- 摘要：This paper demonstrates a real-time coherent optical transmission test at a signal rate of 32×100Gbit/s in the Polarization-Multiplexed Quadrature-Phase-Shift-Keying（PM-QPSK）modulation format over 2 080 km Standard Single Mode Fiber（SSMF）realized on the basis of a 31.786Gbaud/s transponder.It generates 32 WDM channels from a single laser on a 32 GHz grid and yields a spectral efficiency of 3.11b/s/Hz.When it employs 20% FEC limit（BER level of 2E-2）after 2 080 km transmission,the Qfactor still has 1.2dB margin.In addition,it investigates the relationship between filter bandwidth and OSNR penalties of 100Gbit/s PM-QPSK signal.25 htested measurement shows that the system is stable and all the tested BERs are below 1E-2at 1 550 nm WDM channel.关键词：coherent detection;real-time transmission;100Gbit/s transponder;PM-QPSK
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发布时间： - 摘要：This paper first presents an overview of the key technologies for high-rate DWDM transmission systems,including QPSK,8QAM,16 QAM and other novel modulation formats,ultra-low loss optical fibers/Raman amplification and new optical integrated devices.Then it analyzes and compares the different impacts of these technologies on DWDM system transmission.On this basis,it introduces several successful experiments on large-capacity DWDM transmission in recent years,which shows that these technologies have broad prospects of applications.关键词：DWDM transmission;novel modulation format;Raman amplification;optical integrated device
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发布时间： - 摘要：This paper studies the applications of DP-QPSK modulation and the coherent reception technology in low-rate systems and realizes 2.67Gbit/s real-time transmission.Experimental results show that DP-QPSK modulation and coherent reception technology can optimize the OSNR tolerance for Ultra-Long Haul（ULH）optical transmission systems.关键词：DP-QPSK;coherent reception technology;ULH repeaterless optical transmission system
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发布时间： - 摘要：Having many advantages such as high spectrum efficiency and flexibility,Elastic Optical Network（EON）is widely accepted as one of major direction of optical network development and Routing and Spectrum Assignment（RSA）is one of its core technologies.This paper proposes an improved energy-aware RSA algorithm for EON,which considers both network energy consumption and available spectrum resources in routing selection and spectrum assignment.Theoretical analysis and numerical simulation results show that compared with the traditional RSA algorithm,this improved algorithm can improve energy efficiency and reduce traffic blocking rate.关键词：EON;RSA;energy efficiency;traffic blocking rate
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发布时间： - 摘要：This paper first introduces several commonly-used optical layer protection methods for 100Gbit/s WDM networks and discusses their technological essence,advantages and disadvantages.Then,it simulates and analyzes their system performances in connection with the existing network cases.Finally it presents suggestions for the selection of the protection modes for100Gbit/s WDM networks.关键词：100Gbit/s system;WDM;optical layer protection
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发布时间： - 摘要：On the basis of the basic equations describing the propagation variation of optical pulses in optical fibers,this paper first investigates in depth the characteristics of super-Gaussian pulses propagating in conventional single-mode fibers.Then it theoretically analyzes the different factors affecting the position of the narrowest pulse width in the fibers and obtains by simulation the approximate distribution functions of the position of the narrowest pulse width,the initial pulse width,and secondorder group velocity dispersion coefficient.The results indicate that the pulse shape of the incident super-Gaussian pulses without initial chirps into the fiber will no longer remain a single-peak structure,but undergoes a variation from near-rectangular,multi-peak,and finally to single-peak and that the pulse width influenced by chromatic dispersion will go through a process of first narrowing and then broadening.The research on the position of the narrowest pulse width in a fiber is instructive to determining the dispersion compensation position in practical optical communication and optical sensing.关键词：fiber dispersion;super-Gaussian pulse;Single-mode fiber;pulse width;second-order group velocity dispersion
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发布时间： - 摘要：Proposed by the Internet Engineering Task Force（IETF）working group,the Transparent Interconnection of Lots of Links（TRILL）protocol can effectively exterminate the waste of bandwidth and slow convergence in the Shortest Path Tree（SPT）and has multiple advantages such as the shortest path forwarding and equal cost multipath.On the basis of this technology,this paper presents an improved implementation mechanism for TRILL technology,in which it calculates the routing in a centralized way.This mechanism can effectively improve the network capabilities of automatic management and control and meet the need of the data center for layer 2networking.关键词：IETF;TRILL;data center
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发布时间： - 摘要：In access technologies for network security,the IEEE 802.1xprotocol-based authentication method is much superior to other authentication technologies,but it still has some deficiencies in practice.This paper briefly describes the protocol security,analyzes the existing security defects and presents an improvement process and solutions.It effectively avoids the middleman attack and Denial of Service（DoS）attack by improving the Type-Data domain in the messages in the protocol packets.The results show that although the improved protocol may lead to slight increase of the switch CPU utilization rate,it still can reach the filtration rate of as high as 86.3%in large numbers of message attacks.关键词：IEEE 802.1xprotocol;middle-man attack;DoS attack;authentication;network security
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发布时间： -
- 摘要：In order to effectively separate signal from noise so as to accurately locate the fault points in optical cable lines,avoid missing or misjudging the point of failure and improve the positioning accuracy,this paper presents a method for locating and detecting the fault points in communication cable lines.In this method,it eliminates or decreases the noise in Optical Time Domain Reflectometer（OTDR）testing curve by using the theory of supervising the signal singularity with Wavelet Transform Modulus Maxima（WTMM）in connection with the Threshold De-noising Method（TDM）.The results show that using the proposed de-noising method,it is possible to effectively de-noise OTDR test curve and more accurately locate the fault points in cable lines.关键词：wavelet transform;modulus maxima;threshold de-noising;Lipschilz index;fault point
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发布时间： - 摘要：In view of the possible defects resulted from the effects of various factors in the preparation of optical fiber ends,this paper develops a machine vision technology-based fiber end detection system.In the light of the structural features of the microscopic fiber end images,it fits the ellipse in them using the image processing algorithm and proposes a concentric elliptical constraint-based ellipse detection method and picks out the fitting ellipse of fiber core and cladding contour.On the basis of the parameters of the acquired fitting ellipse,it divides the fiber end into three sectors of for regional flaw detection and statistics.All the algorithms are developed and realized by using OpenCV function call in VS2010.Experiments show that this detection system can accurately measurate the quality of optical fiber ends.关键词：optical fiber end;OpenCV;ellipse detection
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发布时间： - 摘要：On the basis of the Power-Current（P-I）characteristic of plastic packaged 10Gbit/s 850 nm VCSEL TOSA at high and low temperatures,this paper investigates the temperature compensation technology for 10Gbit/s SFP+short-range optical modules and presents methods for multiple sampling,calculation and sectional matching and compensating coefficients at different temperatures.The experiment data and analysis results indicate that this method improves the performances of the optical module within the full range of-4085℃,and enhances the index consistency of the module under similar working environment.关键词：10Gbit/s SFP+;VCSEL;temperature compensation;optical power
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发布时间： - 摘要：This paper designs an I2C bus limit test controller for assessing the robustness of the I2C bus communication of optical transceiver modules.In this design,the parameters exceed the limits by a certain range according to the I2C communication protocol.This controller is designed on CPLD using Verilog HDL,which is used to perform two main functions,I2C frequency test and bus line characteristics test.Software simulation and hardware implementation verify the correctness of this design.This controller can also conduct tests of other kinds of I2C slave devices with the only need to change device address,offset address and other relevant parameters.关键词：I2C bus;limit test;Verilog HDL;CPLD
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发布时间： - 摘要：With the nonlinear effects of Fiber Bragg Grating（FBG）ignored,this paper investigates the impacts of the nonlinear effects of single-mode fibers on the output characteristics of FBG FP cavity and derives the mathematical expression for the transmissivity of FBG FP cavity in Continuous Wave（CW）and pulsed laser injection.The results show that the FBG FP cavity exhibits bistable output characteristics in CW injection and ring-down characteristics in pulsed laser injection,and modulation instability emerges.关键词：fiber optics;FBG;FP cavity;cavity ring-down spectrum;nonlinearity
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发布时间： - 摘要：This paper designs a simple-structured low-cost Triple-Wavelength Erbium-Doped Fiber Laser（TW-EDFL）with output wavelengths of 1 530,1 540 and 1 550 nm respectively and a stable output power of 1.5mW.It investigates the relationship between the length of Erbium-Doped Fiber（EDF）,pump power and output power and concludes that the optimum length of EDF is 4.15 mand the optimum pump power is 200 mW.It balances the gain and loss of 3signal lights in the resonant cavity by adding 3Variable Optical Attenuators（VOA）and using the gain equalization method,thus avoiding the mode competition effect of EDF at room temperature.关键词：TW-EDFL;VOA;gain;loss
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发布时间： - 摘要：Wireless quantum communication is characteristic of huge information quantity,transmission instantaneity and good security.On the basis of studying the quantum propagation characteristics in free space,this paper summarizes the entangledstate distribution mechanism of wireless quantum transceivers,and presents a wireless quantum hierarchical network structure suitable for wireless Wide Area Networks（WAN）.Furthermore,for performing channel coding,making its performance close to the system tolerance and converting quantum channel coding into classical coding,it proposes adopting the 3-qubit channel coding,and gives an irregular coding/decoding scheme and analyzes its performances using the EXIT chart.The results indicate that this system architecture is suitable for the future applications of wireless quantum communications.关键词：wireless quantum communication;hierarchical architecture;EXIT chart;irregular coding
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发布时间： - 摘要：This paper studies the joint estimation and compensation algorithm for IQ imbalance and channel estimation for Single-Carrier Frequency Domain Equalization（SC-FDE）and Orthogonal Frequency Division Multiplexing（OFDM）-based60 GHz communication systems.It obtains the optimal solution of Channel Impulse Response（CIR）without knowing the IQ imbalance parameters by minimizing the Channel Residual Energy（CRE）,but once the IQ imbalance parameters are received,the CIR estimation can be obtained by simple substitution calculations.Therefore,the proposed method can separate channels from IQ imbalance for flexible compensation without any restrictions on the training sequence.The simulation results show that this method exhibits good performances for either Line-Of-Sight（LOS）or Non-Line-Of-Sight（NLOS）60GHz channels.关键词：60GHz;SC-FDE;OFDM;IQ imbalance;channel estimation
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发布时间： - 摘要：In view of the nonlinearity problems of RF power amplifiers,a two complex polynomials-based analog pre-distortion circuit is proposed in this paper,and the coefficients of these polynomials are adaptively optimized according to the response of the power amplifier using the LMS algorithms,resulting in the optimum linearity of the power amplifier.This pre-distorter is characterized in simple circuit,little computation and suitability for broadband communications.Furthermore,it is experimentally simulated and tested on the basis of dual-band and WCDMA signals.The results indicate that the pre-distortion linearization method is obviously effective to inhibiting Intermodulation（IM）distortion components and improves the Adjacent Channel Power Ratio（ACPR）to 56.1dB,well compensating the nonlinearity of the RF power amplifiers.关键词：power amplifier;analog pre-distortion;linearization technology;adaptive control;polynomial
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发布时间： - 摘要：This paper constructs a novel two-dimensional（2-D）Optical Orthogonal Code（OOC）named OCFHC/OCS by using the One-Coincidence Frequency Hopping Code（OCFHC）for time spreading sequence and the One-Coincidence Sequence（OCS）for wavelength hopping sequence.Then it analyzes the codeword performances of OCFHC/OCS,obtains its average cross-correlation expression and simulates and compares its BER.Simulation results indicate that when the code weight and the minimum gap between the two adjacent chip wavelengths are fixed,increasing the number of hopping wavelength does not only reduce the BER of OCFHC/OCS system,but also increase the cardinality and compared with OOC/OCS code,the codeword performance of OCFHC/OCS is even better.关键词：OCDMA;2-D OOC;OCFHC;OCS;BER
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发布时间： - 摘要：In routing establishment for Ad hoc networks,Ad hoc On-Demand Distance Vector（AODV）routing protocol adopts flooding forwarding for Route Request（RREQ）messages,which will generate a lot of unnecessary retransmission and may cause broadcast storm,thus affecting the network performances.In view of this problem,this paper proposes an improved scheme based on dynamic probabilistic forwarding,in which it selects different probabilistic forwarding for RREQ messages according to the number of neighbor nodes.The results show that this scheme effectively reduces the network end-to-end delay and improves the network throughtput and packet delivery rate,especially when there are more nodes in the network and the network is dense.关键词：Ad Hoc network;AODV routing protocol;RREQ message;simulation
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发布时间： - 摘要：Although soft-output sphere decoding algorithm can approach to the bit error performance of Maximum Likelihood（ML）algorithm,it has high computational complexity.This paper presents a complexity-reduced soft-output sphere decoding algorithm,which introduces the reduced noise element to the reverse iterative upper triangular matrix Rof QR decomposition algorithm so as to narrow the initial search radius.Then it uses the minimum distance criterion to effectively trim the search tree and narrow the tree search space.MATLAB simulation results show that this algorithm can reduce the system computational complexity to a great extent while approaching to the bit error performance of traditional soft sphere decoding.关键词：LTE-A system;signal detection;soft sphere decoding
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发布时间： - 摘要：In the light of the two-hop characteristics of relay networks,this paper proposes a resource allocation algorithm based on two-hop rate matching for multi-cell relay networks.It first independently allots subcarriers to all the users in every cell within the first sub-slot and builds a non-cooperative game-based power allocation model on the basis of the above allocation results.Then,it matches the second hop rate with the first hop resource allocation result,adaptively allotting resource to relay so as to meet the rate demand of the edge users.Simulation results demonstrate that while meeting the demand of the edge users for rate,the proposed algorithm further improves the throughput of the center users and reduces the system transmitting power,thus improving the system performances.关键词：LTE-A relay network;resource allocation;non-cooperative game;two-hop rate matching
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发布时间： - 摘要：In view of the characteristics of the two-dimensional sparse channel of the time and frequency domains of the LTE-A systems in Doppler environment and in line with the distribution of pilot in the time and frequency domains and its correlation with them,this paper presents an Orthogonal Matching Pursuit（OMP）algorithm-based improved compressed sensing channel estimation by decomposing the search space into ranges between OFDM symbols in time domain and between subcarriers in frequency domain.Simulation results show that the improved OMP algorithm has still lower Mean Square Error（MSE）than the original one.关键词：compressed sensing;channel estimation;OMP
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发布时间： - 摘要：In order to effectively suppress the Multiple Access Interference（MAI）,a novel complementary subtraction technology based on Modified Double Weight（MDW）code is proposed for Optical Code Division Multiple Access（OCDMA）systems.The system performances are compared by using an RZ pulse generator and an NRZ pulse generator in different transmission lengths and bit rates and so are the supplementary subtraction detection technology and the direct detection technology.The system test results show that at a transmission bit rate of 2.5Gbit/s,the novel complementary subtraction detection technology is superior in performance to the Spectral Direct Detection（SDD）technology and it can effectively eliminate the MAI.关键词：OCDMA;MDW code;complementary subtraction technology;SDD technology
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