最新刊期
卷 ， 期 4 ， 2018
- 摘要：To improve the security and optical fiber bandwidth utilization of incoherent Optical Code Division Multiple Access（OCDMA）system,the two-dimensional optical encoder/decoder based on prime code/prime code in p =5 as two-dimensional address code is proposed.Two-dimensional incoherent OCDMA system is analyzed based on OptiSystem platform.The simulation indicates that the two-dimensional incoherent OCDMA system is able to transmit signal successfully.The performance of OCDMA system is deteriorated due to the Multiple Access Interference（MAI）when multiple users exist.Then the method to suppress the MAI is proposed.The simulation results show that MAI can be effectively avoided when optical hard limiters exist.关键词：optical encoder/decoder;two-dimensional incoherent OCDMA system;MAI;system performance
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发布时间： - 摘要：Aiming at the unbalanced flow of the switch managed by the controller in the Software Defined Network（SDN）,a switch migration selection algorithm based on Performance Prediction of Singular Value Decomposition（PSVD）is proposed.By combining the current load and the load at a similar time in the past to predict the load information of the controller in the future,the switch with the maximum resource occupancy is then moved to a target controller that is currently under light load and still under a low load in the future.The experimental results show that this algorithm improves the resource utilization of the controller,realizes load balancing and shortens the response time of the controller.关键词：SDN;load balance;PSVD;switch migration
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发布时间： - 摘要：With the integration of big data in the Software Defined Network（SDN）network applications,a series of Quality of Equipment（QoE）problems are emerging gradually,such as data flow failure which is caused by failure to update the flow table in real time.In order to solve this issue,this paper proposes an algorithm based on stagnation timeout optimization to enhance the availability of OpenFlow switch table resource in a burst load environment.The algorithm can make the data stream and the flow item match smoothly,and then improve the efficiency of data stream forwarding through dynamic balance table flow resource,control resources,and reasonable setting timeout.At the same time,the algorithm seals the flow table entries that are successfully matched with the data flow in the stream table,and effectively improve the survivability of the flow table in time.Experimental results show that the stopping timeout improvement mechanism in the algorithm is more effective than the fixed timeout mechanism in terms of QoE.关键词：SDN;QoE;resource;timeout;data flow
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发布时间： - 摘要：In this paper,a bi-directional Raman amplified unrepeatered system is established,and the nonlinearity compensation algorithm is applied at the receiver side.A 300 km unrepeatered system is experimental demonstrated at 10 Gbaud/s with 16 Quadrature Amplitude Modulation（QAM）format.The simulation and experimental results show that the performance of the system can be improved by 2 dB after nonlinearity compensation.The experiment indicates that the nonlinear compensation algorithm is effective and necessary for the unrepeatered system.关键词：bi-directional Raman amplification;ultra-long span;nonlinear compensation algorithm;coherent optical communication
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发布时间： - 摘要：In this paper,a kind of THz single-polarization single-mode PCF is proposed.The dependence of refractive index matching coupling on several parameters（diameter of the micro air holes d3,lattice constantΛ3,lattice shapes in cladding）are investigated with a full-vector Finite Element Method（FEM）.Simulation results show that the best-optimized parameters of fiber are supposed to be d3 =27.7μm,Λ3=38μm and triangular lattice.The fiber exhibits large polarization-dependent loss ratio（>100）and wide bandwidth（0.281 THz）.The polarization-dependent loss ratio will be larger than 100 when the frequency is higher than 0.719 THz,and single-polarization single-mode transmission is realized.At the frequency of 0.95 THz,the polarization-dependent loss ratio reaches the maximum of 479 and the confinement loss is 2.4 e-3 dB/km.Compared with the liquid filling method,the structural adjustment method achieves larger polarization-dependent loss radio,lower confinement loss,and wider bandwidth.关键词：PCF;THz;single-mode single-polarization;structural adjustment
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发布时间： - 摘要：The tellurite High-Index-Core（HIC）Bragg fibers have been regarded as a new type of photonic crystal fiber,which confine the modes in the core through total reflection and Photonic Bandgap（PBG）.The transmission characteristics of HIC Bragg fiber have been analyzed using the transfer matrix and Bloch theory methods.We design the HIC Bragg fiber with flat chromatic dispersion and low loss of 0.775 dB/m on the 1 064 nm.It is numerically shown that flat chromatic dispersion of HIC Bragg fiber can be generated at the conditions of the filling ratio of d/Λ =0.15,the core radius of R =5μm,refractive-index contrast ofΔn =0.02,the radial multilayer period ofΛ =1.2μm and the cladding layers of N =6.The zero dispersion point is also located at 1 064 nm.关键词：HIC;Bragg fiber;transfer matrix;transmission characteristics;flat chromatic dispersion
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发布时间： - 摘要：Fiber and optical cable is an important area for our country to promote " Broadband China" strategy.In this paper,the global patents in the field of optical fiber and optical cable are taken as the research objects.The trend of patent application and the technology distribution of fiber preform,optical fiber and optical cable are analyzed by using patent analysis methods.The layout and technical characteristics of the main institutions in China and abroad are investigated.Finally,this paper puts forward some suggestions,such as paying attention to patent strategy,strengthening the research and development of key technologies in the future,encouraging the development of innovative technologies for Small and Medium-size Enterprises（SMEs）and creating the agglomeration effect of industries.关键词：optical fiber preform;optical fiber;optical fiber cable;patent analysis;patented technologies;optical communication
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发布时间： - 摘要：In order to develop a strain high Multiple Quantum Well（MQW）laser with high linearity and high power,the strain compensation is theoretically calculated.Metal Organic Chemical Vapor Deposition（MOCVD）process is used to develop the AlGaInAs strain compensated MQW structure.In the final active region,seven sets of tensional strain alternation potential barrier and well layer are used.Since the device adopts the structure of the coplanar electrode,the working current of the laser does not need to pass through the substrate,resulting the reduction of the operating capacitance of laser.The capacitance is reduced when compared with the conventional one and the photoelectric characteristic of the laser is improved.We also fabricate a sample of a strained MQW laser.The Photoluminescence（PL）spectra are obtained by fluorescence analysis.The lasing wavelength is 1 304 nm.The threshold current is Ith ≤9 mA.The slope efficiency of one side is 0.44 W/A.Test results indicate the device has good performance parameters,which has the characteristics of high linearity and high power.关键词：lasers;quantum well;MOCVD;strain compensation;AlGaInAs/InP;coplanar electrode
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发布时间： - 摘要：A 1 550 nm-band Indium Nitride（InN）Distributed Feedback（DFB）semiconductor laser based on the Reconstruction Equivalent Chirp（REC）technology is proposed.Based on the theory of Transfer Matrix Method（TMM）,the optical properties of the structured laser are simulated and analyzed.The results show that the laser designed on the basis of this technology has good optoelectronic characteristics and has a very small threshold current at about 6.1 mA with slope efficiency of0.31 mW/mA.The single-mode lasing at 1 549.09 nm is obtained at an injection current of 20 mA,and the side mode suppression ratio exceeds 39 dB.The effects of laser cavity length and active layer thickness are also analyzed.The longer the cavity length indicates lower power and stronger hole burning effect.The larger active layer thickness indicates higher the threshold current.This result provides some reference value for the design and processing of indium nitride DFB laser.关键词：Semiconductor laser;DFB;InN;REC;TMM
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发布时间： - 摘要：The influence of the doping parameters on the detection wavelength of the GaAs/AlxGa1-xAs Quantum Well Infrared Photodetector（QWIP）is studied based on the theoretical model.In addition,the 2×2 Hamiltonian method is used to calculate the characteristic energy states in this model,which lays a solid foundation for the establishment of the model.By comparing the simulated data with the existing experimental data,it is found that with the increase of doping concentration,the peak normalized absorption rate,absorption coefficient and responsivity width are nonlinearly increased.Finally,it is found that with the increasing of the mole fraction（x）of Al in the AlxGa1-xAs barrier and the inter-subband absorption,the absorbed peak wavelength shifts toward a shorter wavelength.Therefore,it’s significant to select the appropriate doping concentration for the design of high-performance QWIP.关键词：QWIP;Hamiltonian method;mole fraction;doping concentration
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发布时间： - 摘要：Based on the coupled-mode theory and the evanescent field theory,three-layer structure model of the Fiber Bragg Grating（FBG）is proposed and verified through experimental study and reasoning calculation.The sensitivity characteristic of the Bragg wavelength to the refractive index of chemical solution is then obtained.The approximate linear relation between concentration and refractive index is established based on relation theory of concentration and refractive index.The relationships between the concentration and Bragg wavelength of sucrose,ethanol,and Nacl are obtained through analysis.Finally the changes of the Bragg wavelength with the external concentration are obtained by simulations.A chemical concentration sensor is realized with the characteristics of simple structure,small size,good stability,high sensitivity,and free of sensitive components.关键词：FBG;refractive index;concentration of solution;chemical sensor
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发布时间： - 摘要：To enhance the transparency of coupled-waveguide system,this paper analyze the influence of waveguide loss,nonlinearity and the modulation parameters on the system performance.In the approximation of weak-waveguide theory,the nonlinear Schr9 dinger equations are solved numerically by Runge-Kutta method and the results show that with the increase of the coupled-waveguide loss,the transparency of input waveguide will decrease firstly and then increase counter-intuitively.Further results indicate that the power distribution of input waveguide can be enhanced effectively by increasing the nonlinearity of input waveguide.In this way,the effect of transparency is enhanced.Our results are universal for ordinary coupled systems and periodic modulation systems.Therefore,the maximum value of transparency can be obtained through increasing the nonlinearity of input waveguide and coupled-waveguide loss while the input waveguide is modulated periodically with appropriate parameters.关键词：optical communication;periodic modulation system;quantum tunneling
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发布时间： - 摘要：In the next generation optical access network,tunable burst laser is one of the key devices.This paper designs the light path for a tunable burst laser based on electric absorption modulated laser and semiconductor optical amplifier.Common optical components are selected by simulation in ZEMAX to improve the light path and the coupling efficiency.The light path consists of electric absorption modulated laser,semiconductor optical amplifier,optical isolator and lens.The minimum launch power that can be calculated by the simulation.The test results show that this design can meet the requirements of the transmitter in the next generation optical access network.关键词：next generation of passive optical networks;tunable burst laser;electric absorption modulation laser;semiconductor optical amplifier;simulation of light path
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发布时间： - 摘要：In ultra-densely deployed heterogeneous cellular networks,energy efficiency of the network has become prominent due to the increasing number of small cell base stations.In order to reduce the energy consumption and achieve the goal of "green mobile network",an improved user association algorithm based on cell sleeping is proposed to optimize the energy efficiency in this paper.At the same time,some light-loaded base stations which satisfy the cell sleeping criterion according to the interference graph will also switch to the sleeping mode.Finally,the performances of the proposed and conventional algorithms are compared in the simulation.The results show that compared with the conventional alrogithm,the proposed algorithm has much better performance in energy consumption and energy efficiency,achieving the goal of optimizing system energy efficiency.关键词：ultra-dense deployment;user association;cell sleeping;energy efficiency
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发布时间： - 摘要：With the access of mass terminal devices and different business requirements in the Internet of Things,it is necessary to flexibly deploy services within the network.This paper proposes a distributed collaborative network service layout algorithm based on multi knapsack model.By collaborative acquisition of global network through the network nodes,the network modeling layout problem service can be modelled as multi knapsack problem.Therefore,the optimal layout can be obtained.The simulation results show that the reasonable layout of the network service in the network can maximize the network efficiency,improve the utility ratio and the response rate of the node.The proposed method can achieve smooth operation of the Internet of Things and its applications.关键词：Internet of things;service layout;multi-knapsack problem
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发布时间： - 摘要：In view of the limited battery energy in Wireless Sensor Networks（WSN）,this paper proposes a wireless sensor network model supporting wireless charging based on Low Energy Adaptive Clustering Hierarchy（LEACH）algorithm.Firstly,the model of charging and receiving power of sensor nodes is constructed by the principle of magnetic resonance.Then MATLAB is used to simulate the routing protocol algorithm of LEACH.Finally,combining the LEACH algorithm and wireless charging,we propose a new algorithm called New-LEACH,which only performs one-time clustering.The experimental results show that compared with the traditional LEACH algorithm,the new algorithm can effectively improve the life cycle and network throughput of WSN.关键词：WSN;wireless charging;magnetic harmonic resonance;LEACH;New-LEACH
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发布时间： - 摘要：In order to improve the data transmission rate of Visible Light Communication（VLC）system,two kinds of VLC schemes based on space modulation technology are designed and implemented.The transmit end uses Space-Shift Keying（SSK）combined with Pulse Position Modulation（PPM）and Pulse Width Modulation（PWM）respectively to form two complex modulation schemes and transfer data,namely Space Pulse Position Modulation（SPPM）and Space Pulse Width Modulation（SPWM）.As the composite modulation makes full use of space and signal two-dimensional resources,the system band utilization is effectively improved.The current feedback circuit and the voltage amplifier circuit are adopted to improve the dynamic range of the peak level of the receiving level,and the optical pulse is demodulated by the single-chip computer C8051.Based on the hardware and software platform developed in this paper,a four-transmit and one-receive experimental system is obtained.The performance and effectiveness of the system are also tested and verified.关键词：VLC;spatial modulation;bandwidth utilization;single-chip computer
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发布时间： - 摘要：Cellular network based random access process of the Narrow Band Internet of Things（NB-IoT）is much simpler than Long Term Evolution（LTE）.It is also appropriately modified for its features.In this paper,the random access process based on competitive mode in NB-IoT system is analyzed in detail,including coverage level selection,resource allocation,implementation process and so on.At the same time,the newly added suspend and resume process of NB-IoT is systematically studied,and the corresponding flow chart is designed.Based on the TTCN-3 test platform,a conformance test environment is built,and the random access process is tested.The test results are the same as the expected results,which verify the consistency with the standard.关键词：NB-IoT;random access;medium access control;radio resource control
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