最新刊期
卷 ， 期 1 ， 2020
- 摘要：In this paper, an Angle Diversity Optical Receiver Using Two Types of Photo Diodes（PD） with Different Field of View（2FOV-ADR） is designed in an indoor multi-cell Visible Light Communication（VLC） system. It further optimizes the parameters of the receiver with the goal of maximizing Area Spectral Efficiency（ASE）, including the elevation angle of the receiver PD and the combination method adopted. Four combination schemes are considered, namely Equal Gain Combining（EGC）, Select Best Combining（SBC）, Maximum Ratio Combining（MRC）, Minimum Mean Square Error（MMSE） combining. In comparison, the indoor Signal to Interference and Noise Ratio（SINR） distribution and ASE performance of Single PD Receiver（SR） and traditional Angle Diversity Receiver（ADR） are also simulated. It is found that 2FOV-ADR greatly improves the indoor SINR distribution. Compared with the single PD receiver and the conventional ADR, the SINR at the cell edge position is improved by 30 and 20 dB, respectively, and the 2FOV-ADR has the highest ASE at different user numbers. Therefore, 2FOV-ADR can achieve better performance than single PD receivers and traditional angle diversity receivers.关键词：VLC;angle diversity receiver;FOV;optimization
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发布时间： - 摘要：In order to monitor the fiber-optic links in Tibet, which are sparsely populated and have long transmission distances. This paper presents a method of improving the spatial resolution and measuring the distance of a Linear Frequency Modulated（LFM） Optical Time Domain Reflectometry（OTDR）. The method achieves high spatial resolution and large detection distance by generating an intensity modulated analog chirp signal with a frequency range of 200 MHz and a pulse width of 20 μs. Experiments are carried out on the actual fiber-optic transmission link in Tibet using this method. The experiment results show that the method can achieve a spatial resolution of 0.000 53 km on a fiber link with a length of 240 km. And compared with the single pulse OTDR with the same measurement parameters, the dynamic range is improved by 8.5 dB.关键词：OTDR;linear frequency modulation;spatial resolution;dynamic range
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发布时间： - 摘要：To meet the demand of the capacity increase of the Optical Transport Network（OTN） system, and to explore a representative technology evolution direction, China Mobile deploys a long-haul beyond 100 G backbone transmission OTN system over G.654 E fiber in the present network environment. By performing a group of cutting-edge new technologies and organizing field tests, we obtain several useful results including the performance improvement in new fiber, practical transmission distance, multiple channel types for coexistence, energy efficiency, function of online measurement, and etc. Evaluations and specific technical recommendations on the key new technologies are also given as a reference for guiding the subsequent deployment.关键词：optical transmission;backbone OTN;application;G.654E;long-haul;beyond 100 Gbit/s
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发布时间： - 摘要：High Efficiency Video Coding（HEVC） standard puts higher requirements on system bandwidth while improving the coding performance. The traditional electrical interconnection method has the problems of small bandwidth and large delay. Therefore, the high bandwidth and low power consumption of the optical interconnection propose a new solution for on-chip resource data communication. However, due to the limitation of the process level, the integrated optical device cannot be implemented inside the Field Programmable Gate Array（FPGA） chip. Therefore, the off-chip optical device is used to simulate the on-chip optical interconnection system to achieve the purpose of prototype verification. In this paper, based on the BEE4 development platform, the electrical interconnection is used for data communication on a single chip. The optical communication link is built by connecting Quad Small Form-factor Pluggable Plus（QSFP+） optical modules between Xilinx V6 series FPGA chips, and an optical communication network is constructed to realize the prototype of the optical hybrid interconnection network system. Taking the standard test sequence akiyoqcif176×144.yuv with resolution of 176×144 as an example, experimental results show that the optical link can replace the inter-chip electrical communication correctly, and the transmission time between boards is only half of electrical interconnection with integrated frequency of 51.327 MHz.关键词：FPGA;photoelectric hybrid interconnection;prototype system;HEVC
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发布时间： - 摘要：This paper describes the polarization effect mechanism and the vector model analysis of stimulated Brillouin scattering in Brillouin Optical Time Domain Analysis（BOTDA） distributed optical fiber sensing system. Based on current research development, we analyze the polarization-dependent Brillouin gain spectrum, and introduce the control of polarization state and the suppression of polarization fading technology in the stimulated Brillouin scattering effect. Among them, Brillouin fiber sensing system vector modeling analysis and polarization state control technology have a good research prospect. Our analysis has certain reference value in the aspects of using the sensitivity of the polarization state to measure the temperature, strain and vibration information of the distributed sensing fiber and the aspect of suppressing the polarization fading to improve the spatial resolution of the fiber sensing system.关键词：BOTDA;distributed optical fiber sensing;stimulated Brillouin scattering;polarization
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发布时间： - 摘要：Aiming at the interference of the sampled ultra-weak Fiber Bragg Grating（FBG） reflectance spectrum, a high-speed peak seeking algorithm for large capacity ultra-weak sensor networks is proposed. In this algorithm, weight factors are introduced into the least squares fitting method to realize the Weighted Least Squares fitting（WLS） algorithm with optimized fitting coefficient of gaussian curve to locate the center wavelength. Then the central wavelength is modified by Asymmetric Gaussian correction（AG） to achieve high-precision peak location against noise interference. We propose WLS combined with AG（WLS-AG） algorithm. Through experiments, the peak error averages of the least square fitting algorithm, centroid algorithm, WLS algorithm and the WLS-AG algorithm proposed in this paper are compared and analyzed under different noises. The experimental results show that the WLS-AG algorithm works with high Signal-to-Noise Ratio（SNR）. The average error of 20 consecutive repetitive experiments is less than 1 pm, and the mean error is about 10 pm at low SNR. The detection error at different temperatures is within 1 pm, which is the most stable and meets the requirements of ultra-weak FBG sensor system for precision demodulation.关键词：ultra-weak FBG;WLS-AG algorithm;peak seeking algorithm;large capacity ultra-weak sensor network
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发布时间： - 摘要：In this paper, a micro-ring-assisted Mach-Zehnder（M-Z） temperature sensor within micron size is proposed. A liquid micro-ring cavity is coupled to one arm of the M-Z interferometer, and the temperature-sensitive liquid is injected into the cavity based on the microfluidic technique. The temperature change can be detected by analyzing the output spectrum of the sensor. In order to obtain good filtering performances, the arm-length difference of ordinary M-Z filter is usually in the order of millimeters. The arm-length difference of the temperature sensor presented in this paper is only μm micron order. The results show that the proposed sensor has good filtering performances and a temperature resolution. The extinction ratio is more than 10 dB, with 3 dB bandwidth less than 1 nm. The resolution of temperature detection is 0.1 ℃. In addition, the temperature detection range of the sensor can be adjusted by changing the type of liquid in the micro-ring.关键词：microfluidic technique;temperature sensor;M-Z filter;micro-ring resonator
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发布时间： - 摘要：In order to reduce the errors caused by human factors and improve the quality and efficiency of Erbium-doped Optical Fiber Amplifier（EDFA） testing, an automatic testing system based on Python is designed to test EDFA transient quickly. According to the working principle and rate equation of EDFA, a reasonable test method is designed according to the cause of transient in actual optical fiber communication process. The interface bus is used to enable the system to control the multiple test instruments by one computer at the same time. Python is used to realize the automatic control of instruments and equipment, and achieve "one-key" automatic storage of test data and graphics of each instrument and equipment. Experiments show that the system has the advantages of high testing accuracy, easy operation and good scalability, which can fully meet the user’s requirements for transient testing.关键词：EDFA;transient;test system;python
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发布时间： - 摘要：Aiming at the shortcomings of the heavy computational complexity in existing random access preamble algorithm, a 5G random access preamble detection algorithm is proposed. First, the received signal is processed by the inverse process of the transmitting end to obtain a frequency domain preamble. Then a frequency domain ZC sequence is generated and grouped, and the ZC sequences in each group are correlated with the frequency domain preamble. Finally, the threshold is detected by setting a threshold. The sequence uses a multi-antenna diversity combing to modify the Cumulative Distribution Function（CDF） of the relative threshold, and determines an absolute detection threshold. The threshold is a product of the relative detection threshold and the time-varying noise level, based on the relative detection threshold. The simulation results show that compared with the frequency domain fixed threshold preamble detection algorithm, the correct detection probability performance of the proposed algorithm is improved by 1dB in the Additive White Gaussian Noise（AWGN） channel. In the Tapped Delay Line（TDLC300-100） channel, the correct detection probability performance of the proposed algorithm is improved by 2dB.关键词：5G;random access;preamble detection;threshold
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发布时间： - 摘要：Massive Multiple-Input Multiple-Output（MIMO） is one of the key technologies in 5G. Pilot contamination, which is caused by limited number of pilots, has become an important bottleneck for the development of massive MIMO. In this respect, a reasonable pilot allocation should be designed for the valuable pilot resources to reduce the effect of pilot pollution. However, existing pilot allocation schemes mostly consider static pilot allocation, which are not well adapted to the mobile communication environment where user positions are constantly changing. In this paper, a dynamic migration pilot allocation algorithm is proposed for the problem of how pilots are dynamically allocated stepping with the movement of users in massive MIMO. According to pilot allocation algorithm, a user is selected to exchange pilots with the user who has migrated between two time slots and does not change the original allocation pilot for other users. The complexity analysis and simulation results show that the proposed algorithm can significantly reduce the computational complexity and have similar spectral efficiency comparing with the traditional pilot allocation method. Therefore, the proposed algorithm has a high practical significance.关键词：5G;massive MIMO;pilot assignment;pilot contamination;user mobility
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发布时间： - 摘要：The existing Terahertz wireless personal area network dual-channel Media Access Control（MAC） protocol works in WiFi channel and Terahertz channel. Due to the great difference in frequency between the two channels, the coverage of omnidirectional antenna and directional antenna is different, which will greatly reduce the success rate of message transmission among nodes and the throughput of the network as a whole. In addition, in the existing dual-channel MAC protocol of Terahertz wireless personal area network, there is some redundant control overhead, which leads to low channel utilization. This paper proposes a High Efficient Dual-Channel MAC Protocol Based on Relay（HE-BRMAC）in Terahertz wireless personal area network. The HE-BRMAC is divided into relay auxiliary mechanism and adaptive control cost reduction mechanism. Through adaptive control cost reduction mechanism, the control frame is more compact. In this way, the success rate of message transmission can be improved, and the overall throughput of the network can be improved. Moreover, the control overhead can be reduced, and the channel utilization can be improved. It is noted that when the number of nodes is large, HE-BRMAC has more significant effect.关键词：Terahertz;dual-channel;MAC protocol;relay
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发布时间： - 摘要：Visible Light Communication（VLC） with environmental protection, safety and low energy consumption is a powerful complement to the 5 th generation mobile communication. Aiming at the problem of inter-cell interference in multi-cell multi-user Multiple Input Multiple Output VLC（MIMO-VLC） system, a non-imaging receiver based on prism array is uased as the receiving device, and two multi-cell division schemes are proposed to reduce inter-cell interference. The first is a dynamic cell and the second is a non-dynamic cell. The simulation results show that after the Photodetector Selection（PDS）, both schemes can effectively eliminate the influence of inter-cell interference. When the user is in the interference zone, the dynamic cell scheme has better Bit Error Rate（BER） performance at the cost of higher computational complexity. The BER performance of the two schemes is similar when the users are in the non-interference zone.关键词：VLC;MIMO;multi-cell;multi-user;prism array;PDS
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发布时间： - 摘要：Aiming at the problem that the concentrating efficiency and spot uniformity cannot be taken into account in underwater wireless optical communication system, a composite refractive receiving antenna is designed in this paper. The simulation results show that the concentrating efficiency of the traditional Fresnel lens is only 58.725%, while that of the newly designed composite refractive antenna is 86.557%. Moreover, the uniformity of the spot is also good, with the uniformity of 0.659 3 under the condition of ensuring high concentration efficiency. Then the change of focusing efficiency and spot position offset of parallel light source at different incident angles is analyzed. It is found that the focusing efficiency of Fresnel lens is only 3.582 2% at 2 °incident angle, while the focus efficiency of the composite refractive antenna designed in this paper can still reach more than 50% when the incident angle is 1.5 °, and the spot can still be observed when the incident angle is 4 °. The receiving antenna designed in this paper has good reception effect in underwater long-distance wireless laser communication system. Therefore, the receiving antenna designed in this paper is suitable for underwater wireless laser communication environment with high gain and small field of view.关键词：underwater optical wireless communication;compound refractive receiving antenna;Fresnel lens;concentration efficiency
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