最新刊期
卷 ， 期 5 ， 2018
- 摘要：This paper systematically and roundly proposes the seven"technical walls"of network communications technologies we face after decades of exponential growth of the network bandwidth,number of transistors in the chip and number of software codes,including the"technical wall"of wireless mobile communication,IP data communication,fiber communication,Integrated Circuit（IC）,software complexity,big-data processing and energy consumption.These"technical walls"are relatively independent,interactive and itself-systematic.As you know,it is very difficult to turn over a"wall",and it is more difficult to turn over the seven"walls"at the same period.This leads us to think strategically and globally.In addition to developing in the original way（"the trend is becoming smoother","changing growth patterns",or"using new mode,new theory and new method"）,Is there another way to go?Instead of turning to every wall.From the perspective of future development,this path may be Artificial Intelligence（AI）of network communications,will gradually develop for decades or more,from low,intermediate,advanced,to super,so as to compensate for the lack of bandwidth without reaching exponential growth law as a possible way and option.At last paragraph,the network communications may become intelligent and the effect of AI is also given as"network AI body"to solve the operational problem and to greatly raise efficiency uninterruptedly for decades or more.关键词：network communications technologies;technical wall of wireless mobile communication;technical wall of IP data communication;technical wall of fiber communication;technical wall of Integrated Circuit（IC）;technical wall of software complexity;technical wall of big-data processing;technical wall of energy consumption;network AI body
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发布时间： - 摘要：Light Emitting Diode（LED）-based Visible Light Communication（VLC）,combining with communication with illumination,has been attracted much attention recently.The performance of VLC system is mainly subjected to the limited system bandwidth and Signal-to-Noise Ratio（SNR）.However,the previous studies do not make full use of channel resources,especially the SNR resources.In this paper,for the issue of utilization of SNR resource,a time-based hybrid modulation carrierless amplitude phase（CAP）VLC system is proposed.In this system,the real modulation level of the signal can both be an integer a decimal number,which increases utilization of the SNR resources of the channel by grouping bits by a certain ratio.The feasibility and effectiveness of this system are verified through both simulation and experiment.The bit rate can be improved by～10% when peak-to-peak voltage of driving signal ranges from 0.65 Vto 0.86 Vin experimental demonstration.关键词：VLC;CAP modulation;hybrid modulation;LED
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发布时间： - 摘要：As the Fiber Bragg Grating（FBG）sensor network has more and more functions and larger scales,the demand of reliability and scalability is increasing.A novel FBG sensor network based on square sensing unit with multiple ring is proposed.This paper firstly introduces the necessity of adding Optical Switch（OS）to conventional FBG sensor network and then describes the process of construction the network.Then,how the light transmits between the ring channels is illustrated.After that,a Remote Node（RN）is designed,which is used for repairing link faults.Finally,the repair process is analyzed in detail when link fault happens and the scalability of the network is also analyzed in detail.It can be seen that the network is tolerant to one link fault.The results show that the network has good reliability and scalability.关键词：FBG sensor network;OS;reliability;scalability
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发布时间： - 摘要：The application of indoor Visible Light Communication（VLC）network technology in special subway scene is studied.Based on the concept of optical attocell network,a small-cell-covered rectangular network model applied in the subway carriage is constructed,where the user’s interference from adjacent optical Access Point（AP）is fully considered.Strict Fractional Frequency Reuse（sFFR）and Soft Frequency Reuse（SFR）are considered to improve the cell edge spectral efficiency.Furthermore,analytical expressions for Signal-to-Interference-plus-Noise Ratio（SINR）statistics and cell spectral efficiency in the network are derived.Performance of the system is evaluated by comparing spectral efficiency.The results show that the performance of scheme with the reuse factor of 2 is better than other schemes,which can effectively mitigate interference for edge users and improve the edge spectral efficiency.Therefore,based on the original lighting equipment of subway,the Rectangle network and scheme with the reuse factor of 2 should be given priority to construct the VLC network.关键词：VLC;optical attocell network;fractional frequency reuse;subway carriage
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发布时间： - 摘要：The properties of light wave propagation with stochastic scattering in a fiber are particularly attractive because of their influence in various applications.Unfortunately,no accurate theoretical model has been proposed to describe the randomness of the distributions and variations in scattering.In this paper,we propose a model to analyze the random variation in scattering with time and location.Then,we use the model to simulate stochastic scattering in distributed Fiber Raman Amplification（FRA）systems,including Rayleigh scattering and spontaneous Raman scattering,which are crucial limitations in the distributed FRA systems.The power density spectral errors between our simulations and the experimental measurements were within 5 dBc/Hz,rather than the conventional method with more than 10 dBc/Hz errors in high frequency region.It proves the accuracy of our model in describing the stochastic scattering spectra and distributions in FRAs.Our theory is a promising tool for optimizing the performance of distributed fiber systems,especially systems with distributed amplification such as fiber communication systems based on Raman amplifiers and random feedback fiber lasers.关键词：distributed Raman amplification;bi-directional Raman amplification;spontaneous Raman scattering;Rayleigh scattering;random distributed model
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发布时间： - 摘要：In this paper,a weight based Polar code puncturing method is proposed and applied to the image transmission under the Gaussian channel.This method encodes with the same weighted bit of the gray value of the image,and determines the number of deleted bits according to the weighted value of the gray value of the image.The principle indicates that bigger weight means less number of punctured bits and smaller weight means larger number of punctured bits.Peak Signal to Noise Ratio（PSNR）is used to evaluate the performance of reconstructed images.The simulation results show that under the image transmission of Gaussian channel with signal to noise ratio of 6 dB,the PSNR for the improved punctured Polar codes is 18 dB higher than the Polar code with fixed punctured code rate.The performance improvement is more significant at the condition of larger signal to noise ratio.关键词：Polar code;puncturing;image transmission;PSNR
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发布时间： - 摘要：The fiber coil is the core component of the fiber optic gyroscope.Different winding method directly reflects the performance of the gyro.The temperature gradient varies with time will affect the transient characteristics of the fiber coil.For high accuracy fiber coil with octupole-winding method,we first study the transient effects through theoretical analysis and experimental verification respectively.Radial and axial direction temperature excitation model is built with the exist of equivalent asymmetrical length of the high accuracy fiber coil.Then we analyze the thermal nonreciprocal error angle under two different temperature excitation conditions.Next,we experimentally test the thermal nonreciprocal error angle based on the built experimental platform.According to the test result and the theoretical analysis,we can get the equivalent asymmetrical length of the high accuracy fiber coil,analyze the transient effects of high accuracy fiber coil and judge the performance,which are useful for the application of the fiber coil using in fiber optic gyroscope.关键词：fiber coil;equivalent asymmetrical length;octupole-winding method;temperature excitation;thermal nonreciprocal error angle
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发布时间： - 摘要：In this paper,the mathematical model for Optical Fiber Composite Low-Voltage Cable（OPLC）temperature distribution and transmission loss is established considering the effect of temperature change on the transmission performance of OPLC.The model also considers the distribution characteristics of the temperature field of the cable and the difference in the stress expansion caused by different coefficients of expansion of the material.Based on the proposed model,a simulation model of physical field coupling including electric field,light field,temperature field and stress field is designed.Using finite element numerical analysis method and COMSOL Multiphysics simulation software,we analyze the temperature characteristics and light unit transmission loss characteristics of OPLC under steady state and short circuit fault conditions.The simulation results show that the temperature distribution and transmission loss of OPLC are basically consistent with the theoretical calculations in the stable operation state and short-circuit fault state.The optical fiber transmission loss caused by the short-circuit fault shows a steady attenuation trend,which can be neglected in the engineering.关键词：OPLC;finite element method;short circuit fault condition;transmission loss
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发布时间： - 摘要：In order to improve the amplification bandwidth of Raman Fiber Amplifier（RFA）and the transmission capacity of optical fiber communication systems,a broadband RFA with 100 nm bandwidth is designed by using four pumps with different wavelengths.Combined with the particle swarm optimization algorithm when solving the Raman coupled wave differential equation numerically,the wavelengths and powers of four pumps are optimized.The three sets of optimization results with average on-off gains of 18.690 9 dB,19.638 7 dB,21.764 1 dB respectively with corresponding gain flatness of 0.879 7 dB,0.914 4 dB,0.945 2 dB are obtained.Based on the three sets of optimized pump powers and pump wavelengths,the boundary conditions of particle swarm optimization algorithm are improved,which further improve the performance of RFA and particle swarm optimization algorithm.Finally,a broadband RFA with a gain of 22.480 4 dB and a gain flatness of 0.696 3 dB is realized.At the same time,the parameters of inertia weight and learning factors in the algorithm have been appropriately changed so as to analyze and compare how the optimization results change when different parameters are selected.The results of the analysis and comparison provide some references for the choice of algorithm parameters.关键词：broadband RFA;average on-off gain;particle swarm optimization algorithm;gain flatness
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发布时间： - 摘要：According to the rigorous coupled wave theory and the equivalent medium theory,we propose a design and simulation methods for a sub-wavelength guided mode resonant grating filter based on the alumina material.The reflection spectrums of alumina grating in strong and weak modulation system are simulated and analyzed by Rsoft.Also,the influence of structural parameters such as grating period（400～420 nm）,duty ratio（0.2～0.8）and grating thickness（117～367 nm）on the spectral characteristics of grating are investigated.The simulation results indicate that the alumina grating has excellent filtering effect at 610 nm wavelength with the side band less than 3%,FWHM <0.3 nm and high reflectivity（close to 100%）.Finally,we fabricated a alumina resonance filter in the spectral region by fast atom beam etching technology.关键词：sub-wavelength gratings;guided-mode resonance;aluminum oxide;tunable filter
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发布时间： - 摘要：Due to the necessity of simultaneous monitoring of temperature and refractive index,a novel double-parameter sensor based on a composite interference structure has been proposed and demonstrated in this letter.Through cascading Single Mode Fiber（SMF）-Hollow Core Fiber（HCF）-Photonic Crystal Fiber（PCF）,a Fabry-Pérot Interferometer（FPI）and a Mach-Zehnder Interferometer（MZI）are formed simultaneously.Therefore,the change of temperature and Environmental Refractive Index（ERI）can be monitored at the same time by observing the movement of reflection and transmission spectra.The sensitivities of refractive index and temperature can reach up to 127.46 nm/RIU and 52.3 pm/℃,respectively.It is shown certain practical application value by monitoring the environmental refractive index and temperature at the same time.关键词：PCF;refractive index;fiber sensor
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发布时间： - 摘要：An optical switching scheme of graphene based on Optical Tamm States（OTS）is proposed.In this scheme,the OTS are generated at the interface between the metal and the Distributed Bragg Reflection（DBR）using the electronic properties of graphene.The intrinsic wavelength of OTS shifts and the reflectivity of light rises from the lowest point to a high reflection region.By changing the applied voltage,the optical switch can be achieved.The proposed optical switch is simulated by using the Finite Element Method（FEM）and the Time Domain Finite Difference（FDTD）method.The results show that when the incident wavelength is 846.5 nm,the optical switch can be achieved.The insertion loss of the optical switch is 0.88 dB with extinction ratio of 12.7 dB and response time of 1.31 ps.The optical switch has the advantages of low insertion loss and fast response time.It has a good application prospect in the future optical communication system and the optical information processing system.关键词：optical switch;OTS;photonic crystal;graphene
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发布时间： - 摘要：Due to the large impulse noise interference in Laplace noise environment,the performance of spectrum detection is reduced.In order to solve the issue,a robust spectrum sensing algorithm based on exponential absolute value cumulating is proposed.Firstly,it manages the received signal with the exponential absolute value cumulating.This method can compress the impulse noise.It cumulates the signal as the decision statistics.And it can obtain the probability density function of the decision statistics using the central limit theorem and get the threshold.Then it judges whether primary user is using the spectrum.Theoretical analysis and simulation results show that under the same false alarm probability or different signal-to-noise ratio,the detection probability of the proposed algorithm is higher than the detection probability of the absolute value cumulating algorithm and the detection probability of the energy detection with Laplace noise algorithm and the detection probability of the modified absolute value cumulating algorithm.关键词：cognitive radio;spectrum sensing;Laplace noise;theoretical detection threshold;the detection probability
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发布时间： -
Visible-light Indoor Positioning Technology based on the Parameters Optimization of Lambertain Model
摘要：The luminous model of the white Light Emitting Diode（LED）is an important basis for the design of the indoor visible light positioning system.The inaccurate parameters of the luminous model seriously affect the accuracy of the visible light positioning.In order to solve this problem,a method for estimating the order of the Lambertian emission is presented.In this paper,Received Signal Strength（RSS）-based visible light indoor positioning system,which calculates the distance-measuring error between visible light receiver and the visible light transmitter（LED）by adjusting the Lambertain emission order is developed.When the distance-measuring error is minimum,the corresponding Lambertain emission order is considered closest to the reality Lambertain emission order of the LED.Through the simulation indoor scene 5 m×5 m×3 m,the Lambertian parameter optimization method can significantly improve the indoor positioning accuracy of visible light position system.The experimental results verify the feasibility and effectiveness of the Lambertian model parameter optimization method.关键词：LED;visible light communication;Lambertain radiation pattern;indoor positioning;RSS- 6
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发布时间： - 摘要：In cognitive ratio networks,the enthusiasm of Secondary Users’（SU）participation in spectrum sensing is low and the untrusted data is sent from SU to the Fusion Center（FC）due to the poor channel condition.Considering these problems,a cooperative spectrum sensing algorithm based on Reverse Auction Technology（RAT）-Reverse Auction is proposed in this paper.This article refers to the incentive mechanism of RAT.The user is divided into ordinary secondary users and relay secondary users.The use of RAT between these two secondary users encourages the secondary users to participate in the spectrum perception to solve the problem of the lower initiative of SU,and the problem of channel condition difference can be solved by means of relay.The simulation results show that the sensitivity of the proposed method is better than the non-relay method,and the user’s enthusiasm is improved.关键词：cognitive radio;cooperative spectrum sensing;RAT;relay
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