最新刊期
卷 ， 期 5 ， 2017
- 摘要：To satisfy the demand of evolving network business in future access networks,a high speed Mode-Division-Multiplexing Passive Optical Network（MDM-PON）scheme utilizing self-homodyne detection is proposed.In the proposed scheme,one of the spatial modes is used to transmit a portion of signal carrier（namely pilot-tone）as the Local Oscillator（LO）,while the others are used for signal-bearing channels.At the receiver,the pilot-tone and the signal are separated by mode demultiplexer and then sent to the receiver for coherent detection.Due to the low modal-crosstalk Few-Mode Fiber（FMF）and all-fiber mode multiplexer/demultiplexer（MUX/DEMUX）,the pilot-tone and the signal can be effectively separated without Multiple-Input Multiple-Output（MIMO）processing.Compared with Polarization Division Multiplexing（PDM）self-homodyne detection,the spatial efficiency is enhanced.Meanwhile,the self-homodyne detection can effectively suppress the laser phase noise,which relax the requirement for lasers line-width at the Optical Line Terminal or Optical Network Units（OLT/ONUs）.At the receiver side,the Digital Signal Processing（DSP）is also simplified since self-homodyne detection reduces the receiver complexity by eliminating the LO from the coherent receiver,removing the need for frequency offset compensation and reducing the requirement for carrier phase recovery by several orders of magnitude.Using the proposed scheme,aproof of concept 4×40 Gbit/s Orthogonal Frequency Division Multiplexing（OFDM）signal transmission over 55 km FMF using low modal-crosstalk twomode FMF and MUX/DEMUX with error free operation is experimentally demonstrated.Compared with the back to back case,less than 1 dB Q-factor penalty is observed after transmission over 55-km FMF.关键词：PON;self-homodyne detection;MDM;FMF
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发布时间： - 摘要：In order to solve the survivability problem of the distributed data center in energy interconnection,we propose a new resource recovery mechanism,which is data center-oriented.The simulation results show that the strategy realizes the dynamic recovery of the service and improves the response speed of the server,which exhibits high practicality and enforceability for the development of the data center network in the energy interconnection.关键词：energy interconnection;service recovery;SDON
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发布时间： - 摘要：An optimized Digital Background Propagation（DBP）algorithm is proposed and experimentally demonstrated in a bidirectional Raman amplification unrepeated system.The algorithm is achieved by reversely solving the Schr9 dinger equation in electrical domain,which can compensate both chromatic dispersion and nonlinear effects.The proposed algorithm is implemented by optimizing the power curve.An unrepeated transmission of a 10 Gbaud/s Quadrature Phase Shift Keying（QPSK）signal over 320 km single mode fiber is experimentally demonstrated.The experimental results show that the performance is improved by 0.7 dB to 1 dB based on optimized DBP algorithm.关键词：DBP algorithm;bidirectional Raman amplification;unrepeated transmission;coherent optical communication
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发布时间： - 摘要：Fractional vortex light has fractional topology charge,unique radial gap,and relatively many control parameters,which has attracted much attention recently.Based on the diffraction integral theory,the light field expression of fractional order vortex light is derived in the paper.In addition,simulation is conducted on the light intensity distribution and phase distribution with MATLAB.The simulation results show that the radial gap size is related to the decimal part of topological charge value.To be specific,when the decimal part of topological charge value is closer to half integer,the radial gap is more obvious.Moreover,with the increase of the integer part of topological charge,the light spot radius increases.In this paper,a variety of vortex light with topological charge being half integer is produced through reflective type of liquid crystal spatial light modulator.The transmission light spot collected by CCD is consistent with the simulation results of the paper.关键词：fractional vortex;topological charge;radial notch;spatial light modulator
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发布时间： - 摘要：A long-haul optical fiber communication system after 2 000-km fiber transmission with 16-ary Quadrature Amplitude modulation（16 QAM）format is experimental demonstrated.The system uses backward distributed Raman amplification and Digital Background Propagation（DBP）algorithm at the receiver side to compensate the nonlinear effects in fiber transmission.By adapting the distributed Raman amplification,the signal power in the fiber does not decay exponentially.The experiment results show that the proposed DBP algorithm can achieve 2.1 dB improvement of Q2-factor.关键词：coherent optical communication;Raman amplification;DBP algorithm
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发布时间： - 摘要：Since the traditional electric power dispatching data network routing method could not be considered comprehensively by multi-factor,this paper based on the basic theory of Quality of Service（QoS）,combined with the route planning,an integrated routing optimization method based on electric power dispatching data network is proposed.In this method,the service demand and priority relation of dispatching data network are introduced,and the QoS,load and line cost are used as the objective function.It can be used to find the route with low network load and low link cost in the power dispatching data network.The simulation results verify the feasibility of the proposed method by comparing it with the traditional routing strategy.关键词：electric power dispatching data network;routing optimization;QoS;network load
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发布时间： - 摘要：Nowadays,the network address is getting exhausted.How to make more efficient use of limited IP address has become the urgent problem which the telecom operators need to solve.The core idea of Network Address Translation（NAT）is letting a small number of external addresses to represent a large number of internal addresses.This paper uses the design ideas of distributed software and the separation of forward and control to achieve the layering and modularization of NAT function.The implementation of NAT function includes static NAT,dynamic NAT and Port Address Translation（PAT）.Compared with the centralized software design,the main features of this paper include:the separation of forward and control makes NAT more efficiency;the independent management module makes the internal management more convenient and more operational;the distributed multi-process design makes the module has higher protability.关键词：NAT;distributed software;the separation of forward and control;operational;portable
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发布时间： - 摘要：In this paper,we design and realize a music player based on visible light communication technology.At the transmitter side,the STM32 module reads the music files and decodes them,which are sent by LED array.At the receiver side,a lens condenses the light which carries information.A PIN photodiode converts the light into the current.After that,through a trans-impedance amplifier and a filter circuit,the music can be played by a speaker.The system has on-demand function,which can achieve remote wireless control.The test results show that the transmission distance of the signals can be up to 5 m,with clear sound.And the remote control achieves a range of 10 m,which satisfy the requirement of the design.关键词：visible light communication;light emitting diode;audio transmission
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发布时间： - 摘要：400-Gbit/s transmission in single-mode fiber is a hot research topic in fiber transmission system with higher channel capacity.After evaluating the performances of optical fiber transmission systems at 400-Gbit/s per channel,the paper reviews the designs,properties and applications of Low-Loss-Large Effective Area Fibers（LL-LEAF）and Ultra-Low-Loss-Large Effective Area Fibers（ULL-LEAF）in 400-Gbit/s transmission systems.After system transmission tests,network field transmission tests and system equipments cost comparison,LL-LEAFs and ULL-LEAFs are regarded as the optimal optical fibers in"ultra-high speed,ultra-long distance,ultra-large capacity"transmission systems.关键词：transmission;Single-mode fiber;ultra-low loss;large effective area
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发布时间： - 摘要：In order to realize the optical fiber positioning for each pole tower,and monitor the running status of Optical Power Ground Wire（OPGW）more accurately,this paper presents a method of positioning fiber optic cable based on distributed optical fiber sensing technology.By analyzing the real-time monitoring frequency shift data and combining with the structure and erection of OPGW,it is found that the frequency shift of the optical fiber is smaller than that of the mid span due to the connection of the fittings.Therefore,we can identify the location of the tower from the difference and achieve the precise positioning of the transmission line tower.Finally,the feasibility of the location method is verified by referring the line information.关键词：tower;location;OPGW;optical fiber sensing technology;frequency shift
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发布时间： - 摘要：Given that the special requirements for optical fiber in ultra-high High Voltage Direct Current（HVDC）systems,the performance analysis of several special kinds of optical fibers for HVDC transmission measurements and control system is carried out.The optical properties such as the core layer/cladding diameter of the optical fiber,refractive index distribution and the characteristics of flame retardant are studied,providing references for choosing specialty optical fibers with preferable cost performance for the ultra-high HVDC transmission measurements and control system in different application environment.The results indicate that the smaller the core diameter of the fiber,the smaller the attenuation value of the fiber at 850 nm.For the applications in ultra-high HVDC transmission and control system,small-diameter fiber（approximately 62.5μm）tends to be used in the field that the amount of data transmission and are large,and the transmission signal bandwidth is specifically required;large-diameter（approximately 200μm）fiber tends to be used in the field that the power transmission is specifically required.关键词：multimode fiber;core diameter;flame retardant properties;HVDC
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发布时间： - 摘要：A novel Rayleigh Brillouin Optical Time Domain Analysis（RBOTDA）scheme is proposed to deal with the low Signal-to-Noise Ratio（SNR）issue in traditional RBOTDA system.The output power is increased by 2 times than single-ended detection based on balanced detection with Stokes sideband and anti-Stokes sideband information.Due to the noise characteristics of two photodiode input signals,the use of balanced detection increases the noise power by 21/2 and the SNR is also increased by 21/2.The feasibility of the system is verified on 2.4 km optical fiber.It is shown that the signal is improved obviously by using the balanced detection technique.关键词：Rayleigh scattering;BOTDA;balanced detection;signal-to-noise ratio
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发布时间： - 摘要：In order to achieve gain flatness and increase the bandwidth in optical fiber dense wavelength division multiplexing system,we proposed a method to increase the bandwidth by multi-wavelength pump combination,and flat the gain of the Raman Fiber Amplifier（RFA）by cascaded optical fiber.We use different wavelengths of dual pump to pump the same kind of fiber and increase the transmission bandwidth.Linear fitting Raman gain spectrum is applied to achieve pre-amplification and compensation in RFA.Therefore,large light output signal power and good gain flatness are obtained.The transmission bandwidth is doubled compared to the bandwidth of single pump pumping case.The simulation results show that the proposed method can achieve average optical power of 6.2 mW,average gain of 24.48 dB,gain flatness of 0.08 dB,and transmission bandwidth of 25.6 nm.This paper presents a new method to realize gain-flattened broadband RFA.关键词：multi-wavelength pumped RFA;optical fiber cascade;gain flatness;transmission bandwidth
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发布时间： - 摘要：We propose a reconfigurable Ultra-Wideband（UWB）pulse in large scale based on cascaded Dual-Electrode Mach-Zehnder Modulators（DE-MZM）.In the simulation,by adjusting the relative delay between the two RF inputs of DE-MZMs and the bias voltages,the first to fifth order UWB pulses can be generated.Furthermore,the polarity of UWB pulse can be changed by controlling the relative delay between the electrical inputs of DE-MZM.关键词：reconfigurable UWB pulses;DE-MZM;higher-order UWB pulses
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发布时间： - 摘要：Due to the defects of the severe pilot pollution exist in the massive Multiple-Input Multiple-Output（MIMO）system when the same pilot sequences are reused by all cells for channel estimation,the paper proposes an enhanced algorithm for channel estimation to alleviate the pilot pollution.In this paper,previous same pilot sequences are replaced by the random pilot sequences for the channel estimation which has the advantages of more accurate uplink channel status information and lower pilot pollution due to the fact that the random pilot sequences are independent and unrelated.The simulation results of the mean square error of the channel estimation show that the proposed method can obviously mitigate the pilot pollution when comparing with the method with the same pilot sequences.关键词：massive MIMO;same pilot sequence;pilot pollution;random pilot sequence
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发布时间： - 摘要：The features of Generalized Pre-coding aided Spatial Modulation（GPSM）are that in each time slot the bit information of space dimension is transmitted by selecting the active receiving antenna combination.In the same frequency spectrum efficiency and signal-to-noise ratio,GPSM shows better bit error performance when compared to conventional generalized spatial modulation system.Meanwhile,to reduce the complexity of signal detection in GPSM,this paper proposes a group detection algorithm base on GPSM.The simulation results show that the detection performance of the proposed algorithm is similar to that of the Maximum Likelihood（ML）method,while the complexity is reduced significantly.关键词：pre-coding;spatial modulation;bit error performance;group detection
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发布时间： - 摘要：Machine to Machine（M2M）communications are widely used in the existing cellular network architecture.However,due to the huge number of M2Mc ommunication terminals,conflicts,network congestion,delay and other issues may occur when a large number of M2M terminals simultaneously initiate random access requests.In order to solve these problems,this paper proposes a group-based random access mechanism which groups the terminals and sets the priority.And the high priority group terminals can be allocated random access resources preferentially.The simulation results demonstrate that the proposed method can effectively reduce the collision probability,save energy,improve the probability of successful access of the terminal and reduce the time delay.关键词：M2Mcommunications;grouping;access rate;time delay
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发布时间： - 摘要：In view of the data frame obtained by the mobile phone CMOS camera which is regard as the receiver in VLC link,the data frame has a low extinction ration due to the blooming effect of the CMOS.In addition to the background light,the thermal noise of CMOS will reduce the data frame recognition rate.Aiming at the above problems,an optimization method using high-low-hat transformation and maximum value suppression is proposed.This method improves the extinction ratio of the data frame and suppresses the local noise.Therefore,the data frame can be decoded easily.However,the optimization algorithm is time consuming.In order to transplant the algorithm into the mobile phone,the data frame is processed by a short time-Local Weighted Scatterplot Smoothing（lowess）signal recognition method.The results show that the lowess algorithm is less affected by local noise,and the optimal signal to noise ratio can be obtained when compared with previous algorithm.关键词：VLC;threshold segmentation;CMOS camera
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发布时间： - 摘要：To solve the problem of hybrid beamforming in millimeter wave Multiple-Input Multiple-Output（MIMO）system,a hybrid beamforming algorithm based on iterative updating is proposed.The algorithm improves the system performance by improving the correlation between the analog beamforming matrix and the error matrix.Firstly,the proposed algorithm updates the error matrix iteratively.Then,the singular value decomposition of the error matrix is used to obtain the singular value matrix and then an analog beamforming vector is obtained.Finally,the analog beamforming matrix is updated according to the analog beamforming vector.Compared with the traditional Orthogonal Matching Pursuit（OMP）hybrid beamforming algorithm,the performance of the proposed algorithm is better than OMP algorithm and close to that of fully digital beamforming algorithm,especially when the number of data streams and Radio Frequency（RF）link is similar and small.关键词：millimeter-wave;massive MIMO;hybrid beamforming;fully-digital beamforming
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