最新刊期
卷 ， 期 3 ， 2013
- 摘要：The Few-Mode Fiber（FMF）-based Mode Division Multiplexing（MDM） system has currently become a research focus in the world as it can continue to improve the transmission capacity of fiber-optic communication systems.After completing the FMF design,this paper studies the excitation mechanism,characteristics and implementation of three kinds of mode selective excitation techniques,namely offset injection,Long Period fiber Grating（LPG） and Spatial Light Modulation（SLM）,with the focus on SPM-based mode selective excitation technique.关键词：MDM;FMF;offset injection;LPG;SLM
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发布时间： - 摘要：This paper briefly introduces the system architecture of GPON ONU,focusing on the analysis of the common attacks it is liable to and the causes thereof,and offers a concrete solution to attack prevention on the basis of practice.In this solution,the token bucket mechanism limits the packet rate by ONU card to its CPU queue,effectively preventing the impacts on ONU CPU utilization rate from large amounts of protocol messages,thus avoiding the inconvenience caused to the user.关键词：GPON;ONU;attack;network driver;CPU utilization rate
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发布时间： - 摘要：Owing to the dynamic environment of telecommunication networks,simple applications of the Data Mining（DM） technology are not sufficient for timely acquirement of deeper knowledge.This paper first proposes a methodology for the applications in the DM-based real-time status,which converts the telecommunication data into a series of knowledge processes,and then assists the DM flow in real-time environment with an intelligent agent framework.Finally,it carries out a case analysis of the integration of the DM technology for the acquired intelligent agent-based real-time knowledge.Experimental results show that real-time knowledge is the key to the management of telecommunications networks.关键词：real-time data mining;intelligent agent;telecommunication network
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发布时间： - 摘要：All-Optical Wavelength Conversion（AOWC） is a core technology for WDM fiber-optic communication networks.As Four-Wave Mixing（FWM）-based AOWC can maintain the original amplitude,phase and polarization direction of signals,it is appropriate for advanced modulation formats with high spectral efficiency.This paper systematically summarizes the research advances in signal wavelength conversion in various FWM-based advanced modulation formats and compares and analyzes the advantages and disadvantages of various schemes.Finally,it discusses the methods for improving the applicability and reliability of the devices.关键词：AOWC;FWM;advanced modulation format
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发布时间： - 摘要：In face to the QoS requirements of differentiated users,Routing and Wavelength Assignment（RWA） algorithm for supporting differentiated services is a current focus of study.This paper proposes an improved Grouped Wavelength Assignment Strategy（GWAS） for differentiated service-supporting intelligent optical networks,which introduces dynamically adjustable wavelength grouping schemes to achieve differentiated QoS for different levels of services.Simulation results show that the proposed strategy can ensure higher-priority services better performances than lower-priority services.Specifically,with the same service load,the traffic blocking rates of higher-priority services in Mesh and NSFNET networks are reduced by 24% and 18% at the maximum when signals at 9 wavelengths are multiplexed in each fiber and by 15% and 10% when signals at 160 wavelengths multiplexed in each fiber respectively.关键词：intelligent optical network;RWA;differentiated services;GWAS;QoS
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发布时间： - 摘要：In this paper,we study a method for constructing a full-rank Quasi-Cyclic Low Density Parity Check（QC-LDPC） code,which can reduce encoding complexity and improve the performance of Bite Error Rate（BER） while reducing the number of short cycles.Furthermore,we present an improved Belief Propagation（BP） decoding algorithm,in which by selecting the variables node logarithmic likelihood ratio decision threshold T=5.3 and the number of parity node edges q=3,we can improve the decoding performance to a certain extent under the conditions of weak turbulences with different intensity.Our studies show the construction method for LDPC code and the improved decoding algorithm presented in this paper have broad prospects in atmospheric laser communications.关键词：atmospheric laser communication;QC-LDPC code;rank;BP algorithm
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发布时间： - 摘要：On the basis of analyzing the effects of frequency offset on signal constellation,a blind source separation-based carrier residual frequency and phase offset estimation method is proposed.The received signals are first centered and whitened,and the received data points are separated in time by using the initiated separation matrix with random numbers.Then,the separation-,mixed-and global matrixes are estimated using the stochastic gradient algorithm and the variable step size are updated with the PI value estimated on the basis of the global matrix estimation.Finally,the phase change trajectory of the residual frequency offset signals can be estimated on the basis of the relationship between various elements in the separation matrix and consequently the carrier frequency offset size can be estimated from the number of intervals between the adjacent phase jumping points.Simulation results show that this method can effectively estimate the residual carrier frequency offset and stationary phase offset values of the received signals.关键词：frequency offset estimation;phase change;blind separation;variable step size
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发布时间： - 摘要：In order to avoid clock loop in case of multiple types of clock failures in Sync Ethernet,Ethernet Synchronization Messaging Channel（ESMC） messages are extended.On the basis of using the reserved bytes in ESMC messages to transmit the Clock Source ID（CSID） and recording Clock Source Time To Live（CSTTL）,the extended Synchronization Status Message（eSSM） algorithm is presented.This algorithm can not only effectively avoid clock loop in case of multiple types of clock failures,but also optimize clock tree and improve clock performance.关键词：Sync Ethernet;SSM;ESMC;clock loop
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发布时间： - 摘要：As Passive Optical Network（PON） is an important access scheme for next generation access networks,much attention ought to be paid to its energy efficiency,especially when energy shortage has become a serious problem in the world today.1 bit energy is an index for measuring energy efficiency.In PON P2MP networks,the increase or decrease of a single user’s 1 bit energy is not directly dependent on the changes of ONU assess bandwidth as it is also affected by the OLT broadcast effective factor α.Besides,device improvement will lead to bandwidth increase and the reduction of the total consumption of 1 bit energy will enable energy efficiency improvement.关键词：1 bit energy;PON;energy efficiency
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发布时间： - 摘要：Packet Transport Network（PTN） is a unified packet-switching-based,connection-oriented multi-service transport technology.This paper introduces the services & network features of a radio & TV MAN and studies its adaptability to this technology for PTN-based construction.In view of the present conditions and main problems in Handan Radio & TV MAN,it proposes and describes in detail a PTN-based solution to its transformation and summarizes the advantages of such transformation,i.e.satisfying the diversified requirements in terms of network scale,structure and capacity when the enterprise services are growing in high speed.
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发布时间： - 摘要：At present,PON-based FTTx optical access networks are growing rapidly.However,they are facing enormous challenges in terms of maintenance and management and urgently require efficient network maintenance and management tools,especially the methods for service acceptance and fault diagnosis.Starting from the key issues to be tackled in network maintenance and management,this paper briefly analyzes the functional requirements for the integrated test systems for optical access networks and,on this basis,presents the test architecture scheme appropriate for the PON technology-based FTTx optical access networks.关键词：optical access network;PON;test system;fault diagnosis
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发布时间： - 摘要：For the numerical analysis of the loss properties of Photonic Crystal Fibers（PCF）,this paper studies the effects of such structural parameters as air hole diameter,space between air holes and the number of air hole rings in the cladding on the PCF loss properties at 1.31 and 1.55 μm by the multipole method.The results show that the loss can be reduced by choosing structures with high air-fill scale and increasing the air hole rings in the cladding and that it can be dramatically decreased by increasing the outermost air hole diameter while keeping the dispersion property constant.This conclusion provides a theoretical basis for the design of PCF with low loss property.关键词：PCF;loss;multipole method
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发布时间： - 摘要：In this paper,an all Optical Analog-to-Digital Converter（OADC） system is designed and demonstrated,which consists of a high-repetition-frequency laser with low-time-jitter,a Wavelength Division Multiplexer（WDM） and an Optical Time Division Multiplexer（OTDM）.Then,the relationship between the quantification accuracy and sampling rate,and the sampling pulse jitter and the amplitude jitter is given.Finally,the polarization characteristics of this system are analyzed and the measures for minimizing the timing jitter caused by accumulated dispersion and by fiber refractive rate and for suppressing the nonlinear effects of high-power short pulse laser in transmission in fibers discussed.关键词：optical analog-to-digital conversion;polarization;timing jitter;nonlinear effect
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发布时间： - 摘要：A polarization-independent Delayed Self-Heterodyne Interferometer（DSHI） is introduced,the optical system of which is a Faraday Rotator Mirror（FRM）-based Michelson interferometer,and its laser linewidth measurement principle and polarization-independent characteristics theoretically analyzed.On this basis,the polarization state stability measurement for the traditional Mach-Zehnder（M-Z） DSHI and the polarization-independent Michelson DSHI are performed respectively and compared with that for the ultra-narrow（4.5 kHz） laser linewidth.The results indicate that the Michelson DSHI with high polarization state stability has a higher accuracy in laser linewidth measurement.Furthermore,by using this type of DSHI,the linewidth measurement for another ultra-narrow semiconductor laser with a linewith of 1.7 kHz is implemented in an ideal range of accuracy.关键词：linewidth measurement;Michelson interferometer;FRM;DSHI
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发布时间： - 摘要：For the Superstructure Fiber Grating（SFG） consisting of a Fiber Bragg Grating（FBG） and a Long Period Fiber Grating（LPFG）,a similarity transformation method for the coupled mode equations is presented,and the effects of strain and temperature gradients on the transmission and reflection spectra of SFG are investigated.The simulation results show that by the effects of strain or temperature gradient,its reflection spectrum and transmission spectrum corresponding to ν order cladding mode shift independently according to an established rule.On this ground,it is possible to simultaneously calculate the strain and its gradient,or temperature and its gradient at the location of SFG.关键词：superstructure fiber grating;coupled mode theory;strain;temperature change
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发布时间： - 摘要：In order to solve the noise problems of the photoelectric detection system in detecting weak optical signals,this paper designs a photoelectric detection system with a wide dynamic range and automatic shift functions by establishing equivalent circuit models,deriving the output signal-to-noise ratio formula of photoelectric detection circuit,and analyzing the key factors affecting the system noise performance.The experimental results show that this system can detect weak optical signals accurately.关键词：photoelectric detection;weak optical signal;circuit design
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发布时间： - 摘要：A novel low-cost,small-size,handheld pressure-controlled variable lens-based Variable Optical Attenuator（VOA） is designed and fabricated in this paper.With a cylindrical precision tube as the lens chamber sandwiched between an input fiber connector pin and an output-fiber connector pin with external thread,this device has a structure of input-fiber + variable lens + output-fiber.The manual procession of the spiral tube enables the occurrence of compression deformation of the liquid lens so as to achieve the adjustment of the lens focal length,thus controlling the efficiency of the light intensity coupled from the input-fiber to the output fiber and achieving the controllable adjustment of the light attenuation.The experimental results indicate that this VOA attenuates in the range of 360 dB and can be used for such occasions as experimental teaching.关键词：pressure controlled variable lens;VOA;handheld
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发布时间： - 摘要：For the applications of 2-D photonic crystals in optical beam adjustment and deflection,a 2-D photonic crystal-based Polarization Beam Splitter（PBS） is theoretically realized by adopting the FDTD method and perfect matched layer absorbing boundary conditions and introducing an anti-reflection layer in the structure.Optimization calculations show that by adjusting the anti-reflection parameters with the changes of the optical frequency,over 95% of light energy in the TE mode is transmitted and over 95% of light energy in the TM mode is reflected,thus separating the TM mode from the TE mode.Small in size,high in transmittance,large in splitting angle and high in polarization splitting rate,the PBS introduced in the anti-reflection layer is extensively applied in high-density integrated optical communication systems.关键词：2-D photonic crystal;PBS;FDTD method;optimization design
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发布时间： - 摘要：<正>"2013年度中国通信学会科学技术奖励工作会议"于4月24日在北京召开。中国通信学会副理事长兼秘书长、科技奖励工作办公室主任张新生在会议上做了工作报告,对新一届学会领导班子在科技奖励工作方面的思路、规划和部署进行了阐述。工业和信息化部电信研究院于生多副院长、工业和信息化部科技司韩俊
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发布时间： - 摘要：In view of the serious packet loss and energy constraint in the movement of ZigBee wireless sensor networks,a hybrid dynamical cluster routing algorithm based on the ClusterTree+AODVjr protocol is designed on the basis of analyzing the cluster algorithm and the ClusterTree+AODVjr algorithm.By adopting the dynamic cluster mechanism,this algorithm enable the moved nodes to respond in time to the topological changes and rapidly reestablish network connection,thus reducing the packet loss and improving the effective packet delivery rate,while reducing the energy consumption by decreasing flood broadcast of RREQ packet.Simulation results by using network simulator NS2 show that compared with the original ClusterTree+AODVjr algorithm,this improved one can reduce energy consumption by 14% in average and increase average packet delivery rate by 8%.关键词：ClusterTree+AODVjr algorithm;dynamical cluster;energy consumption;packet delivery rate
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发布时间： - 摘要：In the paper,the performances of ultraviolet transmissions in low altitude channels are analyzed by using modtran and a mathematical model for the atmospheric absorption and scattering of near-earth short-range transmissions studied.In a laboratory environment,the system is transmitted by using UV-LED with an angle of view 80° and the scatter transmission of analog signals tested in the range of 58 m.The results show that when a specified effective scatterer is used and the transceiver pitch angle is increased from 10° to 65°,short distance UV scatter transmission can be effectively realized,but when the scatterer density is so large that it is strongly absorptive to UV,the transmission distance will be decreased and single UV-LED transmitting power lowered.However,in practical communication applications,the transmission power and distance can be improved by using LED arrays.关键词：scatter communication;UV;elevation angle;transmission;angle of vision
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发布时间： - 摘要：As the Hybrid Automatic Repeat Request（HARQ） technology can well compensate the effects of wireless mobile channel time-varying and multipath fading on signal transmission,it has become an indispensable key technology for Long Term Evolution（LTE） systems.For the uplink/downlink HARQ process in TD-LTE systems,this paper presents an implementation scheme in Digital Signal Processing（DSP）.The running results in DSP verify the effectiveness and feasibility of this scheme.关键词：LTE;uplink/downlink HARQ process;DSP implementation
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