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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Calculation of Long-Term Tropospheric Attenuation Statistics Using Weather Cubes
摘要： An initial investigation into the use of Weather Cubes compiled using the atmospheric characterization package Laser Environmental Effects Definition and Reference (LEEDR) to calculate long-term attenuation statistics for remote sensing and satellite communication simulations is presented. A Weather Cube is a three-dimensional mesh of numerical weather prediction (NWP) data plus LEEDR calculations that allows for the quantification of rain, cloud, aerosol, and molecular effects at any UV to RF wavelength on any path contained within the cube. This work compares total path attenuation probability of exceedance curves derived using a single profile of numerical predication data to ground based radiometric measurements of slant-path attenuation in the V & W bands as well as relevant International Telecommunication Union Recommendations. The results of this work demonstrate the need for further investigation into this methodology. The use of single profile of numerical weather prediction data to create a Weather Cube does not capture the highest attenuation events which occur at the lowest exceedance probabilities.
关键词： Attenuation Study,Millimeter Wave
更新于2025-09-23 15:21:21
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A measurement of the attenuation of radiation from F-18 by a PET/MR scanner
摘要： The attenuation of 511 keV photons by the structure of a PET/MR scanner was measured prior to energizing the magnet. The exposure rate from a source of fluorine‐18 was measured in air and, with the source placed at the isocenter of the instrument, at various points outside of the scanner. In an arc from 45 to 135 degrees relative to the long axis of the scanner and at a distance of 1.5 m from the isocenter, the attenuation by the scanner is at least 5.6 half‐value layers from the MR component alone and at least 6.6 half‐value layers with the PET insert installed. This information could inform better design of the radiation shielding for PET/MR scanners.
关键词： PET/MR,self-attenuation
更新于2025-09-23 15:21:21
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Features of Wavelet Analysis in X-Ray Reflectometry of Thin Films
摘要： Specific features of the use of wavelet transform for estimating the thickness of layers and their order in a film density profile based on X-ray and synchrotron reflectometry data are considered. Some ways are proposed to reveal the characteristic features of Langmuir film packing by constructing a wavelet transform for the corresponding reflectograms. Dependences of the X-ray attenuation length on the grazing incidence angle are plotted by an example of multilayered box model of film profile; these dependences demonstrate possibilities of mapping the spatial signal delay (which occurs when rays are reflected from layers of different density) in a waveletgram.
关键词： wavelet transform,thin films,attenuation length,Langmuir film packing,X-ray reflectometry
更新于2025-09-23 15:21:01
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Multi-Frequency Estimation of Canopy Penetration Depths from SMAP/AMSR2 Radiometer and Icesat Lidar Data
摘要： In this study, the ?? - ?? model framework is used to derive extinction coefficient and canopy penetration depths from multi-frequency SMAP and AMSR2 retrievals of vegetation optical depth together with ICESat LiDAR vegetation heights. The vegetation extinction coefficient serves as an indicator of how strong absorption and scattering processes within the canopy attenuate microwaves at L and C-band. Through inversion of the extinction coefficient, the penetration depth into the canopy can be obtained, which is analyzed on local (Sahel, Illinois) and continental scale (Africa, parts of North America) as well as for a one year time series (04/2015-04/2016). First analyses of the retrieved penetration depth estimates reveal strongest attenuation for densely forested areas, therefore vegetation attenuation should be accounted for when retrieving soil moisture in these areas. For the continents of North America and Africa penetration depths decrease in average with an increase in frequency from L- to C-band. Moreover penetration depth time series were found to match with expected seasonal variations (e.g. vegetation growth period & rainy season) for analyzed local regions.
关键词： ICESat,Vegetation attenuation,SMAP,AMSR2,canopy penetration,multi-sensor
更新于2025-09-23 15:21:01
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Evaluation of Atmospheric Detrimental Effects on Free Space Optical Communication System for Delhi Weather
摘要： Free Space Optical (FSO) communication systems are gaining popularity due to its tremendous speed, advanced capacity, cost effectiveness, secure and easy to deploy wireless networks. This technology has proven an effective choice for last mile applications and hard to reach areas where deployment of optical fibre links is not feasible. But FSO link is highly weather dependent and as signal passes through the atmospheric channel, the main impairments are the atmospheric turbulence, which induce fading and deteriorate the system performance. Delhi has a great potential for FSO communication because of its clear skies. Since there is no analysis for weather condition found in Delhi, this work provides analysis of typical Delhi weather condition ranging from heavy to light rain, fog and clear sky. The performance of FSO link is analysed in terms of attenuation and link length margin under different weather condition. The results are concluded to identify which atmospheric condition influences more on FSO link performance.
关键词： rain attenuation,atmospheric attenuation,free space optical communication,absorption,scattering,visibility,rainfall rate,Delhi weather condition,fog attenuation,link margin
更新于2025-09-23 15:19:57
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[IEEE 2019 Sixteenth International Conference on Wireless and Optical Communication Networks (WOCN) - Bhopal, India (2019.12.19-2019.12.21)] 2019 Sixteenth International Conference on Wireless and Optical Communication Networks (WOCN) - WIMAX Smart Grid Communication network for a Substation
摘要： This multidisciplinary paper reports on a research application-led study for predicting atmospheric attenuation, and tries to bridge the knowledge gap between applied engineering and atmospheric sciences. As a useful comparative baseline, this paper focuses specifically on atmospheric attenuation under pristine conditions, over the extended terahertz spectrum. Three well-known simulation software packages (‘HITRAN on the Web’, MODTRAN R(cid:13)4, and LBLRTM) are compared and contrasted. Techniques used for modeling atmospheric attenuation have been applied to investigate the resilience of (ultra-)wide fractional bandwidth applications to the effects of molecular absorption. Two extreme modeling scenarios are investigated: horizontal path links at sea level and Earth-space path links. It is shown by example that a basic software package (‘HITRAN on the Web’) can give good predictions with the former, whereas sophisticated simulation software (LBLRTM) is required for the latter. Finally, with molecular emission included, carrier-to-noise ratio fade margins can be calculated for the effects of line broadening due to changes in macroscopic atmospheric conditions with sub-1-THz ultra-narrow fractional bandwidth applications. Outdoors can be far from pristine, with additional atmospheric contributions only briefly introduced here; further discussion is beyond the scope of this paper, but relevant references have been cited.
关键词： molecular emission,atmospheric attenuation,carrier-to-noise,MODTRAN R(cid:13),THz Torch,HITRAN,thermal infrared,transmittance,THz,LBLRTM,molecular absorption
更新于2025-09-23 15:19:57
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Investigation and Analysis of Data Rate for Free Space Optical Communications System Under Dust Conditions
摘要： In this study, the performance of free-space optics (FSO) communication link under dust conditions was analysed. The data were modulated by the non-return-to-zero technique. The optical link was investigated with varying data rates under the effect of dust conditions. The performance of the FSO system was tested in terms of the bit error rate (BER), Q-factor and received power at the maximum link. Simulation results were obtained to compare between two transmit data rates (0.3 and 0.7 Gbps). The system has a high BER at a high data rate. In the meantime, it has a high Q-factor at a low data rate.
关键词： OptiSystem 7.0,Atmospheric transmittance,FSO,BER,Dust concentration,Attenuation,Q-factor,Propagation,WDM
更新于2025-09-23 15:19:57
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Infrared radiation Induced attenuation of radiation sensitive optical fibers: influence of temperature and modal propagation
摘要： We investigate the X-ray (40 keV) and γ-ray (1.2 MeV) radiation responses of three different radiation sensitive Optical Fibers (OFs) up to 100 Gy(SiO2). In particular, we study the Radiation Induced Attenuation (RIA) in the Near Infrared domain (NIR) for single mode OFs doped with Phosphorus (P), Aluminum (Al) and Phosphorus/Cerium (PCe) in their cores at three temperatures up to 50 °C. RIA levels and kinetics strongly depend on the operating wavelength and fiber composition. For both P and PCe-doped fibers, the P1 defects are the main contributors to the RIA, with Ce-codoping inducing a decrease of radiation sensitivity. For the Al-doped fiber, no specific absorption bands can be discriminated in the NIR. Both X- and γ-rays lead to the same RIA levels and kinetics. The RIA spectral dependences on dose and temperature highlight the potential of the three investigated fibers for radiation detection and dosimetry. To better discuss the properties of point defects responsible for the NIR RIA, we analyze how the fundamental mode propagation influences the RIA spectra of each fiber type. By reasonably assuming that the core RIA exceeds largely the cladding RIA and by calculating the mode Confinement Factor (CF), the RIA spectra of the core material are reconstructed and the spectral characteristics of defects are discussed for each type of fibers.
关键词： Radiation Induced Attenuation,Aluminum,Optical fiber,Phosphorus,Cerium
更新于2025-09-23 15:19:57
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Design and Analysis of Variation in Chlorophyll and Depth for Open Ocean Underwater Optical Communication
摘要： The underwate communication is of great interest of research for many researchers because of increased dealings of human beings with world exists underwater. Underwater Commu- cation Technology (UCT) is becoming an important part of communication technologies. These include communication between divers, ships, and network system for autonomous underwater vehicles. However, optical communication with underwater exchange of infor- mation is challenged with many issues. In this paper, the attenuation for optical transmis- sion is obervsed for optical waves that are absorbing inside water, in result, suspending par- ticles and planktons produces optical scattering indirectly. In connection, underwater needs to rectify high attenuation regions for analysing ocean composition affects in Deep Ocean. This produces chlorophyll profiles that identify the attenuation in underwater communica- tion.with high attenuation. In past studies, the constant attenuation is observed irrespective of depth of occean. Furthemore, the paper address, optical attenuation for underwater com- munication via depth dependent. The system is tested for 400–700 nm and 0–250 m depth for chlorophyll concentration profile (S1–S9). The system is demonstrated via GUI devel- oped in Matlab that shows the optical attenuation at different depths underwater and along with that regions with deep chlorophyll maximum (DCM) are also shown.
关键词： Deep ocean depth,Optical attenuation,Deep chlorophyll maximum (DCM),Under water optical communication systems
更新于2025-09-23 15:19:57
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Coupled-mode-induced transparency and attenuation resulting from cross-polarization coupling
摘要： Induced transparency and attenuation effects are observed in the throughput of a single whispering-gallery microresonator due to mode coupling between two coresonant orthogonally polarized whispering-gallery modes of very different quality factors. Intracavity cross-polarization coupling, occurring when either the transverse electric (TE) mode or the transverse magnetic (TM) mode is driven, results in coupled-mode induced transparency or coupled-mode induced attenuation. Coresonance between the TE and TM modes is obtained by strain tuning, and the cross-polarization coupling is produced by polarization rotation due to optical spin-orbit interaction in a slightly asymmetric resonator. The observed behavior enables slow light and fast light, i.e., the delay or advancement of an incident resonant pulse. Experimental results representative of several different types of behavior are presented here. Induced transparency is seen to be accompanied by pulse delay, whereas induced attenuation can involve pulse advancement or delay. The results are analyzed and explained by analytical modeling and by comparison to the output of a more detailed numerical model describing these effects. Delays of up to 170 ns and advancements of up to 14 ns are found. The observed range of cross-polarization coupling strengths (probability of polarization change per round trip), namely, 10?10–10?7, is in agreement with theory.
关键词： slow light,induced transparency,whispering-gallery microresonator,cross-polarization coupling,attenuation,fast light
更新于2025-09-23 15:19:57