最新刊期
      卷 ， 期 1 ， 2007
      • Chen Jingjing,Mao Qian,Liu Guohui
        Issue 1, Pages: 1-3(2007) DOI: 10.13756/j.gtxyj.2007.01.001
        摘要：The Bass model-based forecast for the Internet users in China is studied in this paper.A general description of the Bass model is first made,and then its parameters determined on the basis of the historical data and finally the forecast and error analysis made by using this model.The resulted forecast will give an approximate time when saturation of the Internet users arrives in China,providing a basis for the future bandwidth forecast. At the end,the scope of its applications and the parameter determination methods are given and several schemes for forecast accuracy improvement presented.  
        关键词：Internet;user forecast;Bass model   
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      • Zhao Yongli~1,Cao Miao~2,Zhang Jie~1,Gu Wanyi~1
        Issue 1, Pages: 4-7(2007) DOI: 10.13756/j.gtxyj.2007.01.002
        摘要：In view of the deficiencies of two protection mechanisms steering and wrapping used in RPR,a novel protection mechanism-source node protection is presented and its performances analyzed.Source node protection avoids serious packet loss and reordering existing in steering protection and reduces big latency and unnecessary waste of bandwidth that wrapping protection imports,fully improving the protection performance in RPR.  
        关键词：RPR;steering;wrapping;source node;protection   
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      • Chen Haitao,Deng Tao,Wang Zunzhi
        Issue 1, Pages: 8-10(2007) DOI: 10.13756/j.gtxyj.2007.01.003
        摘要：On the basis of Cross-Phase Modulation（XPM） and Er-doped fiber Nonlinear Amplifying Loop Mirror（NALM）,a novel design scheme is presented for the compression of unchirped Gaussian pulses with low peak power.The numerical simulations reveal that by using this scheme an unchirped optical pulse with 10 ps FWHM can be compressed to an ultra-short pedestal-free and well-amplified pulse with 150 fs FWHM.  
        关键词：XPM;ED-NALM;optical pulse compression   
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      • Xu Xunye,Xiong Zhongzhu,Wang Zhijun
        Issue 1, Pages: 11-14(2007) DOI: 10.13756/j.gtxyj.2007.01.004
        摘要：In this paper,the method for measuring the QoS for VoIP network is introduced and the main elements affecting VoIP QoS performance such as delay jitter,packet loss and IP network delay analyzed.The relationship between its end-to-end voice quality and delay is quantitatively analyzed by using the E-model,the main delay components in the VoIP system pointed out by setting up a mathematical model and the mechanism of their generation and parameters affecting them studied.In the design of a practical VoIP system,it is possible to improve its delay by optimizing these main parameters.  
        关键词：VoIP;QoS of voice;delay   
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      • Yu Jianguo,Xu li,Guo Huazhi,He Liang
        Issue 1, Pages: 15-17(2007) DOI: 10.13756/j.gtxyj.2007.01.005
        摘要：This paper starts with an introduction to the basic principle of Radio over Fiber（ROF） and then presents the multiple applications of ROF technology in future wireless broadband mobile communications,including those in wireless access in multiple systems with heavy loads and in interconnections between the base station and the optical network node equipment in wireless mobile networks.Finally it summarizes the technical advantages of RoF and presents the key technical problems to be resolved.  
        关键词：Radio over Fiber（ROF）;optical network;broadband mobile communication   
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      • Rong Jian~1,Lu Hui~2,Qiang Shijin~3
        Issue 1, Pages: 18-20(2007) DOI: 10.13756/j.gtxyj.2007.01.006
        摘要：Analysis is made of non-directional channels by using site-based iterative modeling,thus obtaining the specific iterative formula.For rooms with furniture,the optical gain formula of LOS is presented.Impulse responses when reflection times k=0,1,2 are simulated by MATLAB programming and the simulation graphics given and explained.In addition,the impulse responses for rooms without furniture in the same conditions are also simulated and compared with those for rooms with furniture,leading to the conclusion that the non-LOS components increase along with the height of the rooms.  
        关键词：indoor wireless optical communication;non-directional channel;site-based iterative modeling   
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      • Ding Tao,Chen Changying,Hu Guoyong
        Issue 1, Pages: 21-23(2007) DOI: 10.13756/j.gtxyj.2007.01.007
        摘要：On the basis of the modification of LSOOC,a new design plan for the address code for the spectral-amplitude-coding optical CDMA（SAC-OCDMA） system is proposed.The characteristics of the code words are analyzed,its comparisons with Hardmard,MQC,MFH,BIBD（m=2） made,tunable Fiber Bragg Grating（FBG） codec designed and the principle of coding and decoding explained.The analytical results reveal that the new code word is large in capacity,simple in coding and decoding and immune from Multi-Address Interference（MAI） when the optical source and channel are ideal.  
        关键词：OCDMA;SAC;LSOOC;MAI;FBG   
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      • Song Shuyan~1,Wu Jun~2
        Issue 1, Pages: 24-26(2007) DOI: 10.13756/j.gtxyj.2007.01.008
        摘要：Nowadays,various kinds of digital home network services have gradually entered homes and different telecom broadband services have been continuously offered.Thus it has become a matter of urgency to realize the effective convergence of these two service platforms.In this paper,we investigate the service platform of home network OSGI and that of NGN.On the basis of their analysis and comparison,we present some considerations about the convergence of these two kinds of service platforms.  
        关键词：home network;NGN;OSGI   
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      • Wang Hongqi,Yang Zhu
        Issue 1, Pages: 27-30(2007) DOI: 10.13756/j.gtxyj.2007.01.009
        摘要：This article introduces the concept of Mid-Stage Access（MSA） and the principle and performance of variable gain EDFA with MSA, analyzes in detail its applications and multiple performances in DWDM systems and its advantages as compared with the conventional fixed-gain EDFA,and predicts the application prospect of variable gain EDFA with MSA.  
        关键词：EDFA;MSA;Variable Gain Amplifiers（VGA）;DWDM;OSNR;DCF;DCM   
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      • Liu Xiaozhi~1,Chen lin~2
        Issue 1, Pages: 31-32(2007) DOI: 10.13756/j.gtxyj.2007.01.010
        摘要：A research scheme for Polarization Mode Dispersion（PMD） automatic compensation in multichannel fiber-optic telecom systems using Particle Swarm Optimization（PSO） algorithm is proposed.As an example,automatic PMD compensation in a two-channel WDM system is numerically simulated and the Degrees of Polarization（DOPs） of the channels before and after the compensation and the variations in the eye diagram obtained.The results indicate that the proposed scheme is effective for multichannel PMD compensations.  
        关键词：WDM;compensation of Polarization Mode Dispersion（PMD）;Particle Swarm Optimization（PSO）;degree of polarization（DOP）   
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      • Sun Baohua,Zhang Minglun
        Issue 1, Pages: 33-36(2007) DOI: 10.13756/j.gtxyj.2007.01.011
        摘要：Based on the in-depth analysis of GPON up-and down-link frame architecture,several factors affecting the bandwidth utilization ratio are revealed.On quantitative analyses,an expression for computing GPON up-and down-link bandwidth utilization ratio is given and its range of variations computed.At the end of the paper,comparison of the bandwidth utilization ratios and costs between GPON and EPON is made,which shows that GPON is more cost-effective.  
        关键词：GPON;EPON;bandwidth utilization ratio   
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      • Fu Yunsheng~1,Chen Xue~1,Hu Jun~1,Wang Chenling~1,Liu Dong~2
        Issue 1, Pages: 37-40(2007) DOI: 10.13756/j.gtxyj.2007.01.012
        摘要：With the growing commercial applications of Ethernet-based EPON and the daily increasing urgency for the interworking tests on equipment from different manufacturers and the EPON system project acceptance test and OAM,we have developed an EPON analyzer.In this paper,its functional requirements are analyzed and its general architecture briefly described,with the emphasis on the design of its hardware platform and the FPGA-based implementation of its core functions.  
        关键词：EPON;protocol analyzing;interoperation test;FPGA   
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      • Wang Hongxia
        Issue 1, Pages: 41-43(2007) DOI: 10.13756/j.gtxyj.2007.01.013
        摘要：As a practical technique in the FTTH system,EPON can optimize the network structure,increase its bandwidth and fully utilize its resources.This paper starts with an introduction to the structure of EPON and the advances in the implementation of voice in EPON.Then it analyzes its support to PSTN and NGN and the protocols it supports and finally it makes a brief analysis of the experimental results so as to prove its advantages.  
        关键词：FTTH;EPON;VoIP   
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      • Zhang Jiantao,Yin Xinda
        Issue 1, Pages: 44-45(2007) DOI: 10.13756/j.gtxyj.2007.01.014
        摘要：This paper introduces an optical power meter for PON system measurement.With specially designed optical and electrical circuit structures,The power meter satisfies the specific requirements for optical signal power measurements in PON systems i.e.simultaneous and online measurements of three optical signal wavelengths in the line and the burst measurement of（1 310 nm） optical signal,thus greatly facilitating the installation,management and maintenance of the system.  
        关键词：PON;simultaneous measurement;on-line measurement;burst measurement   
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      • Liu Daosheng
        Issue 1, Pages: 46-47(2007) DOI: 10.13756/j.gtxyj.2007.01.015
        摘要：As TD-SCDMA technology for 3G systems gradually becomes mature and 3G licenses are about to issue,the construction and optimization of wireless networks and wide applications of TD-SCDMA repeaters are indispensable.This article introduces a simple and practical method for implementing the synchronization and handover of TD-SCDMA repeaters.  
        关键词：3G;TD-SCDMA repeater;synchronization and handover   
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      • Liao Lifang,Zhang Jingsong,Li Wenyao
        Issue 1, Pages: 48-49(2007) DOI: 10.13756/j.gtxyj.2007.01.016
        摘要：The collection of hydrological data using General Packer Radio Service（GPRS） technology is one the communication approaches chosen by hydrological departments.This paper describes the composition of GPRSbased hydrological data collection system,analyses the principle of data transmission between workstations and concentrators/collectors,introduces the design methodology of the application software used in workstations of the monitoring center,and gives the design diagram of the main interface of the workstation application software.  
        关键词：GPRS;hydrological data;data collection;software design   
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      • Zou Jianhua,Wang Jingli,Chen Heming
        Issue 1, Pages: 50-53(2007) DOI: 10.13756/j.gtxyj.2007.01.017
        摘要：The dispersion compensation of one-dimensional （1-D） photonic crystals is studied in this paper.According to the transfer law of the electromagnetic field at the interface of periodic media,the reflectivity of optical waves at different frequencies in 1-D photonic crystals with periodically linear variations is analyzed by using transfer matrix method.The result shows that such photonic crystals have different delay characteristics for optical wave components at different wavelengths.On the basis of such delay characteristics,a novel dispersion compensator for DWDM systems can be manufactured  
        关键词：1-D photonic crystal;linear variation;dispersion compensation;total reflection   
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      • Shi Huiping,Li Hongqiang
        Issue 1, Pages: 54-56(2007) DOI: 10.13756/j.gtxyj.2007.01.018
        摘要：The life of optical fiber cables is determined by the life of their filling compounds and the fibers in them.In their long-term operations,they can hardly be immune from water and humidity,which affect the lives of both the fillings and the fibers.Therefore,the water immergence performance of the cable is one of the most important indexes in terms of its quality,and also an important item in assessing its environment characteristics and an important factor ensuring its life（2530 years）.In this paper,we explore the impact of water immergence on the life of cables and the effective measures for minimizing such impact.  
        关键词：optical fiber cable;water immergence;life   
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      • Liang Qing
        Issue 1, Pages: 57-59(2007) DOI: 10.13756/j.gtxyj.2007.01.019
        摘要：The principle of single-wedge crystal waveplate depolarizer is introduced and its performance analyzed by simulation with the help of Stokes vectors.Two-wedge crystal waveplate depolarizer is proposed and a comparison is made between these two types of depolarizers.The simulation results show that wedge crystal waveplate depolarizers can depolarize an optical beam completely when the diameter of the beam and the angle of the waveplate satisfy a certain relationship and the beam diameter required by the two-wedge depolarizer is only half of that by the single-wedge depolarizer.An application example of connection of an optical fiber to a two-wedge depolarizer is given at the end of this paper.  
        关键词：depolarizer;degree of polarization（DOP）;crystal waveplate   
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      • Zheng Hongjun~
        Issue 1, Pages: 60-63(2007) DOI: 10.13756/j.gtxyj.2007.01.020
        摘要：In this paper,we investigate the temporal waveform,phase,time-bandwidth product of the short pulses（10GHz） before and after their propagations in dispersion-flattened fibers by using a novel method for measuring and analyzing their characteristics,compare them with the linear propagation characteristics of the hyperbolic secant and Gaussian pulses resulted from numerical calculations and evaluate more exactly their temporal waveform and frequency chirp,which further verifies the reliability and accuracy of the new method for the second-harmonic frequency-resolved optical gating.  
        关键词：fiber optics;temporal waveform;frequency-resolved optical gating;time-bandwidth product;dispersion-flattened fiber   
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      • Yu Chunping~
        Issue 1, Pages: 64-66(2007) DOI: 10.13756/j.gtxyj.2007.01.021
        摘要：In this paper,a novel Microelectromechanical System（MENS）-based Optical Tunable Filter（OTF） is introduced,its basic principle and structure analyzed,its optical characteristics investigated and a prototype prepared.The resulted OTF is characteristic of compact size（51 mm×16 mm×10 mm）,easy control and good optical performance（3 dB bandwidth approximately 0.3 nm）.Finally,its applications in EDFA are studied.  
        关键词：MEMS;OTF;EDFA   
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      • Zhang Xue~1,Wang Feng~2
        Issue 1, Pages: 67-70(2007) DOI: 10.13756/j.gtxyj.2007.01.022
        摘要：Predistortion is one of the main linearization techniques used in 3G power amplifiers（PA） at present.In this paper,a double loop analog predistorter scheme is introduced,its theoretical and practical inference and verification conducted,problems in current experimental circuits analyzed and the possible remedies presented.The testing results show that for a 3G PA,IMD3 improvement is over 20dB and ACLR improvement using WCDMA signals is nearly 5dB,which basically fulfills the specification requirements.  
        关键词：predistortion;power amplifier;linearization;double loop controlled;PM distortion   
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