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Modeling of Short-Range Ultraviolet Communication Channel Based on Spherical Coordinate System
摘要： The study on short-range ultraviolet (UV) communication (UVC) channel modeling is often based on prolate-spheroidal coordinate system in previous studies. In this letter, we propose a single scattering coplanar model based on spherical coordinate system, where the transmitter beam and receiver field of view (FOV) can point arbitrarily under the limitation that the sum of transceiver elevation angles and half of their own FOV is less than 180°, and the transmitter beam and receiver FOV are above ground. We utilize the number of intersections between a special ray on the transmitter cone and the receiver conical surface to distinguish the UVC scenarios, which makes the analysis of UVC channel modeling comprehensible. Meanwhile, we validate the proposed model in comparison with the single scattering model and the Monte Carlo simulation model through numerical calculations. The results show that the proposed model agrees well with the both models. This work presents a new method to estimate the path loss of short-range UVC and provides guidelines for the experimental system design.
关键词： ultraviolet communications,Atmospheric propagation,free-space optical communication
更新于2025-09-23 15:22:29
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Parallelized and adaptive square-root unscented Kalman filter for carrier recovery in satellite-to-ground coherent optical communications
摘要： An adaptive square-root unscented Kalman filter with a parallelized architecture for carrier recovery is proposed in QPSK based satellite-to-ground coherent optical communication systems. A new observation model is raised in the proposed scheme to make the state estimation more accurate. The process noise covariance (Q) and the measurement noise covariance (R) are adaptively estimated to make them consistent with their theoretical covariance. For verification of the feasibility of the proposed scheme, corresponding simulations of carrier recovery in satellite-to-ground laser links are carried out and compared with the scheme that is based on linear Kalman filter (LKF). The simulation results demonstrate that, compared with parallelized LKF, the proposed scheme has a wider range of block size and laser linewidth options, and it can relax the required transmit power by up to 0.5-3 dB under different zenith angle at the same BER. Moreover, the proposed scheme can achieve high estimation accuracy and fast tracking capability simultaneously in the case of dynamic frequency offset with better tolerance against the initial errors in Q and R.
关键词： Atmospheric propagation,Adaptive Kalman filter,Free space optical communication,Coherent communications,Carrier recovery
更新于2025-09-23 15:19:57
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Turbulence-induced power drops as extreme events
摘要： Free-space optical communication links through the atmosphere are degraded mainly by the action of scintillation and beam wander. Both phenomena are responsible for fiber coupling misalignments at the receiver. Henceforth, the signal is corrupted by random power drops, which can be identified as extreme events, with particular statistical properties. In this work, we performed experiments and simulations to gain insight into understanding these extremes events and their relation with scintillation and wander at a receiver. Particularly, this sequence also inherits the same long term correlations of the original data.
关键词： Atmospheric propagation,Atmospheric optics,Turbulence
更新于2025-09-19 17:15:36
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Numerical Investigation on the Influence of Water Vapor Ionization on the Dynamic and Energy Deposition of Femtosecond Ultraviolet Laser Filamentation in Air
摘要： The e?ects of water vapor ionization on the nonlinear propagation of femtosecond laser pulses with a 248 nm wavelength are numerically investigated in this paper. It is found that ionization of H2O molecules plays a signi?cant role in air ionization, which seriously a?ects the dynamic and energy deposition of ?lamentation. The propagation of femtosecond pulses in air with di?erent humidity levels are compared. The total number of electrons and total deposited pulse energy increase with the humidity increases. However, they tend to be saturated in high humidity conditions. Results presented here are conducive to characterizing the long-range propagation of ?laments under atmospheric conditions.
关键词： multiphoton absorption,atmospheric propagation,self-focusing,water vapor,ultrafast nonlinear optics
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - High Brightness 2.1 μm Direct-Diode Laser Module
摘要： Direct diode lasers at 2 μm provide the opportunity for more compact sources that can perform similar tasks that are currently undertaken by solid state lasers operating in this wavelength. Infrared countermeasure, gas detection and atmospheric sensing are but a few examples. A high brightness mid-infrared direct-diode laser diode module is presented as a compact source for atmospheric propagation. Optomechanical design enables spatial beam combining to produce excellent combined beam quality deteriorating based only on the performance of each emitter and number of emitters used. The following study showcases the optomechanical design and development of six one-tab C-mount GaSb 2.1 μm single emitter diodes in a module featuring a right-angled staircase spatial beam combining technique.
关键词： GaSb,spatial beam combining,atmospheric propagation,2 μm,Direct diode lasers
更新于2025-09-12 10:27:22
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Fiber Optic and Atmospheric Optical Communication || Optical Wave Propagation
摘要： Electromagnetic (EM) wave plays a key role in modern communication systems, radio and optical, including optical telecommunication systems. Therefore, fiber optic or laser communications emphasize the EM phenomena described mathematically by Maxwell’s unified theory, which we will consider in detail subsequently. Investigation of optical communications started just after the invention of the laser in 1960. Atmospheric propagation of optical waves was investigated parallelly with improvements in optical lasers and understanding of the problems of optical wave’s generation both in the time and space domains. Thus, problems with weather, line-of-site (LOS) clearance, beam spreading and bending in the real atmosphere consisting of gaseous structures (aerosols, fog, smoke, turbulence, etc.), and hydrometeors (snow, rain, clouds, etc.) eliminated free-space optical communication as a major aspect in wireless communication.
关键词： Optical Wave Propagation,Maxwell’s Equations,Atmospheric Propagation,Electromagnetic Waves,Fiber Optic Communication
更新于2025-09-11 14:15:04
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[IEEE 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Xuzhou (2018.7.21-2018.7.24)] 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Study of Propagation of Airy Array Vortex Beams in Turbulent Atmosphere
摘要： A circular phased-locked Airy beam array carrying orbital angular momentum (OAM) propagating through turbulent atmosphere is investigated in detail. The results testify that the OAM modes generated by the array are closely associated with the number of beamlets, requiring the number of beamlets at least twice more than the values of the OAM signal precisely. Furthermore, through multiple-phase-screen simulations, it is shown that the anti-jamming performance of an Airy beam array is significantly enhanced.
关键词： Atmospheric optics,Atmospheric propagation,Airy array vortex beam
更新于2025-09-04 15:30:14