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arXiv 2024年

作者： Zhang, Yufei Chen, Ziyang Guo, Hong State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Center for Quantum Information Technology Peking University Beijing100871 China

Time transfer plays a dispensable role in many fields including navigation and positioning, geodesy, and fundamental tests. However, in certain scenarios where effective relay node deployment is often not feasible, such as harsh environments with extremely poor infrastructure and emergency conditions, effective time transfer without inline amplifiers becomes crucial. In this situation, the maximum transmission distance is limited by the receiver’s measurement capability, particularly its ability to amplify the signal. Here we propose a theoretical model, giving a technical lower bound of the detected signal stability at different transmission distances, induced by limited gain-bandwidth products. The results under common gain-bandwidth products show that while for shorter transmission distances, stability is mainly limited by the background noise of the time interval counter, for longer distances reaching the scale of 300 kilometers, the technical lower bound is below the level of 10 nanoseconds without any inline amplification devices. Therefore, the given technical bound offers guidance on managing the balance between distance and stability, together with the optimization of the receiver in long-distance time transfer without inline amplification. © 2024, CC BY.

关键词： Geodesy

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Continuous-variable Quantum key Distribution Access Network

Continuous-variable Quantum Key Distribution Access Network

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Progress in Electromagnetic Research Symposium (PIERS)

作者： Tao Wang Yuehan Xu Lang Li Xu Liu Zicong Tan Peng Huang Guihua Zeng State Key Laboratory of Advanced Optical Communication Systems and Networks Center of Quantum Sensing and Information Processing Shanghai Jiao Tong University Shanghai China

ISBN: (数字)9798350375909

ISBN: (纸本)9798350375916

Quantum key distribution (QKD) networks are crucial for the development of quantum networks and the early stages of the quantum internet, enabling unconditional secure key distribution and guaranteeing data security. However, current QKD networks are still limited in their structure, and are hard to achieve super multi-user access due to high system costs associated with the original point-to-point QKD system. In this paper, we introduce two cost-effective continuous-variable QKD (CV-QKD) access network schemes. The first one is a round-trip multi-band CV-QKD access network. Specifically, the frequency division multiplexing (FDM) technology is used to support multi-user access, and the round-trip optical architecture is adopted to realize low cost. As a result of the encoding properties of CV-QKD, different users can utilize the quadrature components in various frequency bands to transmit key information. The proposed network theoretically supports hundreds of users and can be easily expanded using simple equipment. The second one is a CV-QKD access network based on directed detection. With the help of the Kramers-Kronig relation, the receiver at the optical network unit can obtain the quadrature components just using a photodetector. Besides, it can also solve the practical issues in the plug-and-play structure. Compared with a quantum access network based on the point-to-point QKD system, these two schemes can provide cost-effective solutions for the subsequent large-scale verification and implementation of quantum access networks.

关键词： Costs optical network units Photodetectors optical receivers Encoding Quantum key distribution Frequency division multiplexing

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Hierarchical Codebook Design Using Scale-Changeable Reconfigurable Holographic Surfaces in Near-Far Field communications

Hierarchical Codebook Design Using Scale-Changeable Reconfig...

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IEEE Conference on Global communications (GLOBECOM)

作者： Shupei Zhang Boya Di Hongliang Zhang H. Vincent Poor State Key Laboratory of Advanced Optical Communication Systems and Networks Peking University Beijing China Department of Electrical and Computer Engineering Princeton University USA

ISBN: (数字)9798350351255

ISBN: (纸本)9798350351262

Reconfigurable holographic surfaces (RHSs) have been proposed as a cost-effective and power-efficient solution for extremely large-scale arrays, where the amplitude of electromagnetic waves radiated at each element is controlled to achieve high directive gain. However, the complexity of acquiring real-time channel state information (CSI) required for beamforming is prohibitively high, especially when the near-field expansion brought by the large-scale RHS is considered. In this paper, we propose a codebook-based beam training scheme for a large-scale RHS-enabled communication system to bypass CSI estimation. Unlike traditional phase-controlled arrays, the amplitude-controlled property of the RHS implies that each RHS element can be selectively activated. This motivates an array reconfiguration method where a scale-changeable RHS array is constructed to generate gain-flat beams with different coverage in the angle-range domain. A hierarchical RHS codebook is then proposed where the coverage of the codewords in each layer is progressively refined. To address the substantial beam search overhead in the near-far field, a two-stage beam training scheme is performed in the proposed codebook, thereby reducing the overhead to a logarithmic level of the element number. The simulation results show that the proposed scheme performs better than phased arrays given the same input power in terms of sum rate, and it also approaches the upper bound achieved by the exhaustive search at a significantly reduced overhead.

关键词： Training Phased arrays Upper bound Surface waves Simulation Electromagnetic scattering Estimation Real-time systems Complexity theory Global communication

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Placement of High Availability Geo-Distributed Data Centers in Emerging Economies

TechRxiv

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TechRxiv 2023年

作者： Liu, Ruiyun Sun, Weiqiang Hu, Weisheng The State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Jiao Tong University Shanghai200240 China

The data center markets in emerging economies are being built at a furious pace. When high availability is required, as it always is in the modern digital economy, the placement of geo-distributed data centers may be influenced by factors such as technician shortage and under-developed infrastructure, both of which are typical in emerging economies. Although the data center availability subject in general has been well studied, it remains unclear how rapid and unbalanced economic development in emerging economies may affect the availability of geo-distributed data centers and their cost of ownership. In this paper, we incorporate the unbalanced availability of infrastructure and technician into the data center placement. The problem is first formulated as a mixed integer nonlinear program (MINLP).To solve this potentially large scale problem, we transform it into a QCQP, capable of handling heterogeneous workloads. The resulting problem can then be efficiently solved by off-the-shelf optimization toolboxes. With real-life data in China, we show how unbalanced development of infrastructure and technician shortage may affect the placement of data centers, and analyze the tradeoff between cost and availability. Our results indicate that technician shortage and unbalanced network infrastructure will lead to increased cost and distinct data center placement strategies. © 2023, CC BY.

关键词： Costs

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Intensity-Modulated Refractometer with Long-Period Fiber Gratings Near Turn-Around Point for Low Refractive Index Detection 20

Intensity-Modulated Refractometer with Long-Period Fiber Gra...

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20th International Conference on optical communications and networks, ICOCN 2022

作者： Hua, Ziyang Zhao, Yunhe Wang, Wei Tang, Mengxue Liu, Yunqi He, Zuyuan Institute of Logistics Science and Engineering Shanghai Maritime University Shanghai201306 China Shanghai University Key Laboratory of Specialty Fiber Optics and Optical Access Networks Shanghai200444 China Shanghai Jiao Tong University State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai200240 China

ISBN: (数字)9781665458986

ISBN: (纸本)9781665458986

We demonstrate a novel intensity-modulated refractometer based on long-period fiber gratings (LPFGs) in thin core fiber (TCF) near turn-Around point. The correlation of contrast to surrounding refractive index (RI) for TCF-LPFGs with different index modulations in the low RI region was investigated. Compared with low index modulation, TCF-LPFGs with high index modulation have a larger sensing region and relatively higher sensitivity. With the index modulation of 4.5x10-4, a high sensitivity of-17.42 dB/ RIU and-163.32 dB/RIU was achieved in the RI region of 1.0-1.20 and 1.24-1.30, respectively. The proposed TCF-LPFGs based refractometer has potential application for low RI detection fields. © 2022 IEEE.

关键词： Refractometers

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Linewidth Compression of a Widely Tunable Hybrid Laser Through High-Q Resonance Feedback

Linewidth Compression of a Widely Tunable Hybrid Laser Throu...

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2024 Conference on Lasers and Electro-Optics, CLEO 2024

作者： Siyu, E. Li, Xinhang Guo, Yuyao Fan, Yihao Jin, Minhui Li, Yu Stroganov, Anton Lu, Liangjun Chen, Jianping Zhou, Linjie State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Key Lab of Navigation and Location Services Department of Electronic Engineering Shanghai Jiao Tong University Shanghai200240 China SJTU-Pinghu Institute of Intelligent Optoelectronics Pinghu314200 China LIGENTEC SA Bâtiment L EPFL Innovation Park Ecublens1024 Switzerland

We present a III-V/Si3N4 widely tunable hybrid laser with an intrinsic linewidth of 50 Hz by using a resonance feedback from a high-Q ring resonator. The linewidth is reduced by approximately 24 fold. CLEO 2024 ©... 详细信息

ISBN: (纸本)9781957171395

关键词： Linewidth

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20736-NODE WEIGHTED MAX-CUT PROBLEM SOLVING BY QUADRATURE PHOTONIC SPATIAL ISING MACHINE

arXiv

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arXiv 2023年

作者： Ye, Xin Zhang, Wenjia Wang, Shaomeng Yang, Xiaoxuan He, Zuyuan State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Jiao Tong University Shanghai200240 China

To tackle challenging combinatorial optimization problems, analog computing machines based on the nature-inspired Ising model are attracting increasing attentions in order to disruptively overcome the impending limitations on conventional electronic computers. Photonic spatial Ising machine has become an unique and primitive solution with all-to-all connections to solve large-scale Max-cut problems. However, spin configuration and flipping requires two independent sets of spatial light modulators (SLMs) for amplitude and phase modulation, which will lead to tremendous engineering difficulty of optical alignment and coupling. We report a novel quadrature photonic spatial-Euler Ising machine to realize large-scale and flexible spin-interaction configuration and spin-flip in a single spatial light modulator, and develop a noise enhancement approach by adding digital white noise onto detected optical signals. We experimentally show that such proposal accelerates solving (un)weighted, (non)fully connected, 20736-node Max-cut problems, which offers obvious advantages over simulation and heuristic algorithm results in digital computers. Copyright © 2023, The Authors. All rights reserved.

关键词： Heuristic algorithms

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基于最先进的光钟直接演示自旋压缩引起的计量增强

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Science Bulletin 2024年第10期69卷 1359-1361页

作者：陈景标于得水 State Key Laboratory of Advanced Optical Communication System and NetworkSchool of ElectronicsPeking UniversityBeijing 100871China National Time Service Center Chinese Academy of SciencesXi’an 710600China Key Laboratory of Time Reference and Applications Chinese Academy of SciencesXi’an 710600China

Benefiting from the recent progress in precise engineering of quantum states and sub-10 mHz linewidth lasers,the stability and accuracy of optical atomic clocks have reached and even exceeded the 1018 level,surpassing their microwave counterparts by over two orders of magnitude[1,2].These advances lead to an anticipated redefinition of the international system of units(SI)second in terms of an optical reference transition as early as 2026.

关键词： optical 光钟自旋压缩

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Distributed Reservoir Computing Based Nonlinear Equalizer for Vcsel Based optical Interconnects

SSRN

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SSRN 2023年

作者： Zhang, Songte Zhang, Wenjia Du, Jiangbing He, Zuyuan State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Jiao Tong University Shanghai200240 China

We propose a distributed reservoir computing based nonlinear equalizer for 106 Gbps VCSEL based optical interconnects. By comparing with neural network and Volterra series based equalizers, the computational complexity of this proposed nonlinear equalizer is significantly reduced in the training, prediction and inference process. 106 Gbps PAM4 short-range optical transmission is demonstrated by experiment, using a VCSEL-based co-packaged optical transmitter to verify the performance of the equalizer and key parameters that affect the nonlinear compensation performance are carefully investigated. We believe that by incorporating such simplified nonlinear equalizers, it is possible to compensate for nonlinear impairments while preserving the inherent advantages of VCSEL-based optical interconnects. This optical interconnect will become a promising paradigm to overcome I/O performance penalty when communication leaving packages. © 2023, The Authors. All rights reserved.

关键词： Equalizers

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Deep Neural Network Enhanced Chip-on-board Hybrid-Packaged Photonic-Electrical Silicon Transceiver for High-speed optical Interconnects

Deep Neural Network Enhanced Chip-on-board Hybrid-Packaged P...

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CLEO: Science and Innovations in CLEO 2024, CLEO: S and I 2024 - Part of Conference on Lasers and Electro-Optics

作者： Qin, Jun Yang, Qipeng Han, Changhao Zhou, Yan Zhang, Yunhao Wu, Yichen Sun, Yu Lu, Junde Liu, Siming Li, Yueqin Sun, Jian Min, Miao Hu, Weiwei He, Zhixue Wang, Lei Yu, Shaohua Shu, Haowen Wang, Xingjun Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument Beijing Information Science and Technology University Beijing100192 China State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Peking University Beijing100871 China Department of Electrical and Computer Engineering University of California Santa BarbaraCA93106 United States Peking University Yangtze Delta Institute of Optoelectronics Nantong226010 China Peng Cheng Laboratory Shenzhen518055 China State Key Laboratory of Information Photonics and Optical Communications BUPT Beijing100876 China

We explore implementing a multilevel deep neural network to enhance the performance of a 4-channel photonic-electrical hybrid-packaged silicon transceiver. Stable transmission and reception of 150 Gbps/λ PAM4 signals... 详细信息

关键词： optical interconnects

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