- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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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) - Transforming the Fiber-Optic Network into a Dense and Ultrasensitive Seismic Sensor Array
摘要： We show a technology capable of performing position-resolved measurement of nanostrain perturbations along a conventional optical fiber cable, with meter-scale resolution. This technology can be deployed in already existing networks to achieve a dense and ultrasensitive seismic sensor array. Applications ranging from seismic protection to chemical sensing are explored.
关键词： seismology,distributed fiber optics sensors,Rayleigh scattering,optical time domain reflectometry,distributed acoustic sensors
更新于2025-09-23 15:22:29
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[IEEE 2018 14th International Wireless Communications & Mobile Computing Conference (IWCMC) - Limassol, Cyprus (2018.6.25-2018.6.29)] 2018 14th International Wireless Communications & Mobile Computing Conference (IWCMC) - Contrasting MISO Schemes for IM/DD FSO Communications with Photon-Counting Receivers
摘要： In this paper, we consider the problem of Multiple-Input-Single-Output (MISO) Free-Space Optical (FSO) communications with intensity-modulation and direct-detection (IM/DD). Unlike the commonly adopted Gaussian-noise approximation, we adopt the exact Poisson statistics for the number of photons falling on the receiver. In particular, we compare three popular MISO schemes; namely, repetition coding (RC), optical spatial modulation (OSM) and spatial multiplexing (SMux). For each one of these schemes, we derive the optimal maximum-likelihood (ML) decoder and we contrast the schemes in terms of rate, performance, complexity, channel state information requirements and tolerance to channel estimation errors.
关键词： Free space optics,spatial modulation,maximum likelihood,repetition coding,spatial multiplexing,MIMO
更新于2025-09-23 15:22:29
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Field Water Balance Closure with Actively Heated Fiber-Optics and Point-Based Soil Water Sensors
摘要： While traditional soil water sensors measure soil water content (SWC) at point scale, the actively heated fiber-optics (AHFO) sensor measures the SWC at field scale. This study compared the performance of a distributed (e.g., AHFO) and a point-based sensor on closing the field water balance and estimating the evapotranspiration (ET). Both sensors failed to close the water balance and produced larger errors in estimated ET (ETε), particularly for longer time periods with >60 mm change in soil water storage (?SWS), and this was attributed to a lack of SWC measurements from deeper layers (>0.24 m). Performance of the two sensors was different when only the periods of <60 mm ?SWS were considered; significantly lower residual of the water balance (Re) and ETε of the distributed sensor showed that it could capture the small-scale spatial variability of SWC that the point-based sensor missed during wet (70–104 mm SWS) periods of <60 mm ?SWS. Overall, this study showed the potential of the distributed sensor to provide a more accurate value of SWS at field scale and to reduce the errors in water balance for shorter wet periods. It is suggested to include SWC measurements from deeper layers to better evaluate the performance of the distributed sensor, especially for longer time periods of >60 mm ?SWS, in future studies.
关键词： soil water storage,actively heated fiber-optics,soil water balance
更新于2025-09-23 15:22:29
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Characterizing the Performance of the NIRC2 Vortex Coronagraph at W. M. Keck Observatory
摘要： The NIRC2 vortex coronagraph is an instrument on Keck II designed to directly image exoplanets and circumstellar disks at mid-infrared bands L′ (3.4–4.1 μm) and Ms (4.55–4.8 μm). We analyze imaging data and corresponding adaptive optics telemetry, observing conditions, and other metadata over a three-year time period to characterize the performance of the instrument and predict the detection limits of future observations. We systematically process images from 359 observations of 304 unique stars to subtract residual starlight (i.e., the coronagraphic point-spread function) of the target star using two methods: angular differential imaging (ADI) and reference star differential imaging (RDI). We ?nd that for the typical parallactic angle (PA) rotation of our data set (～10°), RDI provides gains over ADI for angular separations smaller than 0 25. Furthermore, we ?nd a power-law relation between the angular separation from the host star and the minimum PA rotation required for ADI to outperform RDI, with a power-law index of ?1.18 ± 0.08. Finally, we use random forest models to estimate ADI and RDI post-processed detection limits a priori. These models, which we provide publicly on a website, explain 70%–80% of the variance in ADI detection limits and 30%–50% of the variance in RDI detection limits. Averaged over a range of angular separations, our models predict both ADI and RDI contrast to within a factor of 2. These results illuminate important factors in high-contrast imaging observations with the NIRC2 vortex coronagraph, help improve observing strategies, and inform future upgrades to the hardware.
关键词： planets and satellites: detection,instrumentation: adaptive optics
更新于2025-09-23 15:22:29
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou, China (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - Coherent Detection of Terahertz Waves with a Gas Plasma
摘要： We demonstrate an alternative coherent detection technique via terahertz induced second-harmonic (TISH) in a laser-induced plasma for terahertz waves. In this method, the probe beam requires neither high voltage bias nor optically field bias.
关键词： gas plasma,terahertz detection,Ultrafast nonlinear optics
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Information and Communication Technology Convergence (ICTC) - Jeju (2018.10.17-2018.10.19)] 2018 International Conference on Information and Communication Technology Convergence (ICTC) - Performance of SIM/S-QAM FSO Systems with Phase Errors in Gamma-Gamma Turbulence Channels
摘要： In this paper, we study the performance of subcarrier intensity modulation (SIM) squared quadrature-amplitude modulation (S-QAM) free-space optical (FSO) communication systems considering the atmospheric turbulence-induced phase error in fading channel. The atmospheric fading channel is modeled by Gamma-Gamma distribution while the Tikhonov model is used for the turbulence-induced phase error. The numerical results quantitatively show the impact of atmospheric turbulence parameters to the performance of FSO systems in terms of average symbol-error probability (ASEP) and the power penalty. Besides, the theoretical results are validated through Monte Carlo simulation to confirm our analysis.
关键词： Free-space optics (FSO),Phase error.,Atmospheric Turbulence,Fading Channel,Squared quadrature-amplitude modulation (QAM)
更新于2025-09-23 15:22:29
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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) - Offsetting Self-Phase Modulation in Optical Fibre by Sinusoidally Time-Varying Phase
摘要： We report on our recent experimental and theoretical results on the use of a sinusoidally time-varying phase to suppress undesirable self-phase modulation of optical pulses propagating in fibre-optic systems.
关键词： phase modulation,nonlinear fibre optics
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Particle Measurement Volume and Light Intensity in a Shadowgraph Imaging System
摘要： A method is sought to find the measurement volume instrument for particle measurement is sought. The study shows that the measurement volume depends on a combination of the optical homogeneity of the illumination light and the camera system. The result from a mix of illumination cases and positions shows that, if the true size and the background brightness are known, the measurement volume can be determined with an average precision of four percent using a dual term exponential fit. Using a lens with lower magnification increases the measurement volume since both the field of view and the depth of field increase. However, a larger field of view increases the required amount of light as well as the sensitivity to other optical errors.
关键词： shadowgraphy,optics,LWC,meteorology,Machine vision
更新于2025-09-23 15:22:29
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Majorization preservation of Gaussian bosonic channels
摘要： It is shown that phase-insensitive Gaussian bosonic channels are majorization-preserving over the set of passive states of the harmonic oscillator. This means that comparable passive states under majorization are transformed into equally comparable passive states by any phase-insensitive Gaussian bosonic channel. Our proof relies on a new preorder relation called Fock-majorization, which coincides with regular majorization for passive states but also induces another order relation in terms of mean boson number, thereby connecting the concepts of energy and disorder of a quantum state. The consequences of majorization preservation are discussed in the context of the broadcast communication capacity of Gaussian bosonic channels. Because most of our results are independent of the speci?c nature of the system under investigation, they could be generalized to other quantum systems and Hamiltonians, providing a new tool that may prove useful in quantum information theory and especially quantum thermodynamics.
关键词： quantum channels,majorization theory,passive states,gaussian bosonic channels,quantum optics
更新于2025-09-23 15:21:21
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Cooling atomic ions with visible and infra-red light
摘要： We demonstrate the ability to load, cool and detect singly charged calcium ions in a surface electrode trap using only visible and infrared lasers for the trapped-ion control. As opposed to the standard methods of cooling using dipole-allowed transitions, we combine power broadening of a quadrupole transition at 729 nm with quenching of the upper level using a dipole allowed transition at 854 nm. By observing the resulting 393 nm ?uorescence we are able to perform background-free detection of the ion. We show that this system can be used to smoothly transition between the Doppler cooling and sideband cooling regimes, and verify theoretical predictions throughout this range. We achieve scattering rates which reliably allow recooling after collision events and allow ions to be loaded from a thermal atomic beam. This work is compatible with recent advances in optical waveguides, and thus opens a path in current technologies for large-scale quantum information processing. In situations where dielectric materials are placed close to trapped ions, it carries the additional advantage of using wavelengths which do not lead to signi?cant charging, which should facilitate high rate optical interfaces between remotely held ions.
关键词： trapped ions,laser cooling,quantum optics
更新于2025-09-23 15:21:21