- 标题
- 摘要
- 关键词
- 实验方案
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[IEEE 2018 11th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP) - Budapest (2018.7.18-2018.7.20)] 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP) - FSO Communication for High Speed Trains: Blind Data Detection and Channel Estimation
摘要： We consider an free-space optical (FSO) system for high-speed trains where the sampling clock offset is randomly changing and the receiver does not have any information on the instantaneous channel fading coef?cient. Based on the use of multiple samplers at the receiver, we propose a novel sequence blind detection method, thus without requiring any pilot symbol. Furthermore, using the detected data, we propose a channel estimation scheme for the considered system.
关键词： Free-space optical communications,atmospheric turbulence,time synchronization,data detection
更新于2025-09-10 09:29:36
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Pointing errors effect on fiber coupling efficiency for Gaussian-beam wave through atmospheric turbulence channel in FSO links
摘要： In this paper, we theoretically study the pointing errors effect on fiber coupling efficiency for Gaussian-beam wave with consideration of atmospheric turbulence. A numerical expression of the average fiber coupling efficiency is derived based on mutual coherence function of Gaussian-beam wave and effective transmitter parameters. Numerical results show that the coupling efficiency can be evidently degraded by the pointing errors and pointing errors effect also changes optimum design parameter. And other factors, such as path length and the refractive index structure constant, are also analyzed. It is anticipated that this work is helpful to investigate pointing errors effect on optical wave propagation in the atmospheric turbulence.
关键词： Optical communications,Pointing errors,Free-space optical communications,Fiber coupling
更新于2025-09-09 09:28:46
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DuFiNet: Architectural Considerations and Physical Layer Studies of an Agile and Cost-Effective Metropolitan Area Network
摘要： Metro networks are becoming considerably important to support existing and future 5G services and they are facing new challenges. To address the new requirements, we present a novel, highly flexible and low-cost, filterless Metro network that overcomes existing architectural limitations of filterless solutions. In particular, we detail architectural aspects of this architecture at network and node level as well as the protection strategy. Finally we introduce a novel physical layer modeling tailored for Metro, to assess the capacity and scalability of the transport platform.
关键词： physical layer modeling,filterless network architecture,metropolitan area networks,optical communications
更新于2025-09-09 09:28:46
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Transfer of Highly Stable Frequency Signals on a 150 km Fiber-Optic Communications Line
摘要： The results are presented for the study of an installation for transmission of a highly stable frequency signal with relative instability no greater than 4·10–17 on a ? ber-optic communications line over a distance of 150 km. The installation uses external modulation of laser radiation and active electronic compensation of phase noise. The installation makes it possible to provide synchronization or time scale comparison of mutually separated time and frequency standards that are a component of the highest-category time and frequency standards.
关键词： active electronic compensation of phase noise,highly stable frequency signal,time-and-frequency standards,? ber optical communications line
更新于2025-09-09 09:28:46
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A solid (state) success
摘要： James McKenzie reflects on the impact of the solid-state laser, a device in its infancy when it became the subject of one of the first articles in Physics World. The article discusses the evolution of solid-state lasers from their early days to their widespread use in various applications such as compact discs, DVDs, Blu-ray discs, and optical communications. It also speculates on the future of solid-state lasers and their continued relevance in emerging technologies.
关键词： compact discs,DVDs,Blu-ray discs,solid-state laser,optical communications,diode laser
更新于2025-09-09 09:28:46
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Metasurfaces for independent manipulation of the wavefronts in the different states of phase change materials
摘要： Metasurfaces have attracted increasing attention due to their extraordinary capability in the arbitrary control of electromagnetic waves. However, most metasurfaces lack flexibility and only enable fixed optical performance once fabricated. In this work, we propose ultra-thin metasurfaces with varied functionalities using phase change materials (PCMs) when phase change occurs on whole structured PCMs, which has not been found in previous reports. The wavefronts in the amorphous and crystalline states of the PCMs can be arbitrarily and independently modulated with high efficiency (～60% and ～40% in the two states, respectively). This work may be valuable for information encryption and optical communications.
关键词： wavefront manipulation,metasurfaces,information encryption,phase change materials,optical communications
更新于2025-09-09 09:28:46
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Atmospheric turbulence mitigation using spatial mode multiplexing and modified pulse position modulation in hybrid RF/FSO orbital-angular-momentum multiplexed based on MIMO wireless communications system
摘要： In this paper, the capacity of a free-space optical (FSO) communication over radio frequency (RF) could potentially be increased by the simultaneous transmission of multiple orbital angular momentum (OAM) based on spatial mode multiplexing (SMM) as an additional effective degree of freedom (EDOF) and quadrature amplitude modulation (QAM). This paper describes using hybrid RF/FSO-OAM based on multiple-input multiple-output (MIMO)/SMM using M-ary modified pulse position modulation (MPPM) and spatial PPM (SPPM) for potentially enhancing capacity in wireless communication systems. We present an analytical system design concerning OAM multiplexing and MIMO/SMM processing in free space communications channel under atmospheric turbulence (AT). Here, we assume a new architecture that closes the gap in speeds between millimeter-wave (mm-wave) wireless and optical links. In this study, we highlight recent advances in the use of OAM multiplexing for high-capacity FSO and mm-wave communications. We have developed the MPPM in FSO communication over RF using the source Gaussian model and SMM by proposing a new version of hybrid SPPM and MPPM. The novelty approach presents performance enhancement of the acquisition, pointing, tracking position and AT mitigation of link. We propose to use SMM combined with OAM-QAM based MIMO communications system to mitigate both weak and strong turbulence distortions. Simulation results show that the capacity of OAM-based MIMO system outperforms the capacity of the conventional MIMO system when the propagation distance is larger than a specific threshold. The use of transmitter lenses could enhance the OAM beams with a larger mode spacing (MS) of 2 (OAM l +1, l +3, l +5, l +7 transmitted) shows a lower power penalty (PP) when the inter-channel crosstalk overwhelms a larger lateral displacement of about 2 mm. Using the lenses at the transmitter to focus OAM beams could reduce power loss and PP in OAM-based FSO links and that this improvement might be more significant for higher-order OAM beams and provide high power-efficiency. With a larger of the transmitter and receiver 8 cm, 10 cm aperture size respectively, the system with mode spacing of 2 (OAM l +1, l +3, l +5, l +7 transmitted) and mode spacing of 3 (OAM l +1, l +4, l +7, l +10 transmitted) of OAM beams based on MIMO should fulfill lower-power penalty of 2.2 dB, 3.4 dB, as respectively and could enhance system robustness under angular error but degrade tolerance of lateral displacement. The proposed system provides an excellent signal-to-noise ratio (SNR) for the capacity in the regime of strong atmospheric turbulence. In this way, the maximization of FSO communication and RF wide, the data capacity enhancement, and it is considered a massive solution in the bandwidth provision for future access networks. This work could be beneficial to the practical implementation of OAM-MIMO/SMM multiplexed RF/FSO links.
关键词： Multiple-input multiple-output,Spatial mode multiplexing,Orbital angular momentum,Free space optical communications,Millimeter-wave communications,Modified pulse position modulation
更新于2025-09-04 15:30:14
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Propagation of Optical Coherence Vortex Lattices in Turbulent Atmosphere
摘要： Propagation properties in the turbulence atmosphere of the optical coherence vortex lattices (OCVLs) are explored by the recently developed convolution approach. The evolution of spectral density distribution, the normalized M2-factor, and the beam wander of the OCVLs propagating through the atmospheric turbulence with Tatarskii spectrum are illustrated numerically. Our results show that the OCVLs display interesting propagation properties, e.g., the initial Gaussian beam distribution will evolve into hollow array distribution on propagation and ?nally becomes a Gaussian beam spot again in the far ?eld in turbulent atmosphere. Furthermore, the OCVLs with large topological charge, large beam array order, large relative distance, and small coherence length are less affected by the negative effects of turbulence. Our results are expected to be used in the complex system optical communications.
关键词： optical coherence vortex lattices,evolution properties,atmospheric turbulence,free-space optical communications
更新于2025-09-04 15:30:14
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Direct-Detection Single-Sideband Systems: Performance Comparison and Practical Implementation Penalties
摘要： There is a growing research interest towards high-capacity communication systems for inter data-center (~80 km) communications. While coherent systems are a mature and high-performance technology, their cost is still very high compared to simpler direct-detection solutions. Recently, advanced digital signal processing (DSP) techniques, such as Single Side-Band (SSB) transmission and Kramers-Kronig (KK) receivers have been proposed to increase both spectral efficiency and reach of such direct-detection systems. Apart from the DSP techniques, the main drawback of these solutions is the requirement of a strong (i.e. several decibels higher than the signal) carrier added at the transmitter. This solution inevitably decreases the resulting signal-to-noise ratio (OSNR) and potentially increase the impact of fiber Kerr non-linearities. In this contribution, will provide further insights on the practical implementation penalties which arise from the addition of such carrier in the framework of single-sideband DMT solutions. In particular, we will focus on the modulator biasing technique to add such carrier.
关键词： single-sideband,Kramers-Kronig,direct-detection,intra-datacenter,optical communications
更新于2025-09-04 15:30:14