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THREE-DIMENSIONAL SOUND PROPAGATION MODELS USING THE PARABOLIC-EQUATION APPROXIMATION AND THE split-step fourier METHOD

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JOURNAL OF COMPUTATIONAL ACOUSTICS 2013年第1期21卷 1250018-1250041页

作者： Lin, Ying-Tsong Duda, Timothy F. Newhall, Arthur E. Woods Hole Oceanog Inst Dept Appl Ocean Phys & Engn Woods Hole MA 02543 USA

The split-step fourier method is used in three-dimensional parabolic-equation (PE) models to compute underwater sound propagation in one direction (i.e. forward). The method is implemented in both Cartesian (x, y, z) and cylindrical (r, theta, z) coordinate systems, with forward defined as along x and radial coordinate r, respectively. The Cartesian model has uniform resolution throughout the domain, and has errors that increase with azimuthal angle from the x axis. The cylindrical model has consistent validity in each azimuthal direction, but a fixed cylindrical grid of radials cannot produce uniform resolution. Two different methods to achieve more uniform resolution in the cylindrical PE model are presented. One of the methods is to increase the grid points in azimuth, as a function of r, according to nonaliased sampling theory. The other is to make use of a fixed arc-length grid. In addition, a point-source starter is derived for the three-dimensional Cartesian PE model. Results from idealized seamount and slope calculations are shown to compare and verify the performance of the three methods.

关键词： split-step fourier algorithm underwater sound propagation 3-D PE

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Generation of time-dependent ultra-short optical pulse trains in the presence of self-steepening effect

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Chinese Physics B 2009年第2期18卷 624-629页

作者：钟先琼向安平 Department of Optoelectronic Technology Chengdu University of Information Technology

Starting from the extended nonlinear Schrodinger equation in which the self-steepening effect is included, the evolution and the splitting processes of continuous optical wave whose amplitude is perturbed into time related ultra-short optical pulse trains in an optical fibre are numerically simulated by adopting the split-step fourier algorithm. The results show that the self-steepening effect can cause the characteristic of the pulse trains to vary with time, which is different from the self-steepening-free case where the generated pulse trains consist of single pulses which are identical in width, intensity, and interval, namely when pulses move a certain distance, they turn into the pulse trains within a certain time range. Moreover, each single pulse may split into several sub-pulses. And as time goes on, the number of the sub-pulses will decrease gradually and the pulse width and the pulse intensity will change too. With the increase of the self-steepening parameter, the distance needed to generate time-dependent pulse trains will shorten. In addition, for a large self-steepening parameter and at the distance where more sub-pulses appear, the corresponding frequency spectra of pulse trains are also wider.

关键词： nonlinear optics self-steepening effect ultra-short optical pulse trains split-step fourier algorithm optical perturbation

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Assessment of Intrachannel Nonlinear Compensation for 112 Gb/s Dual-Polarization 16QAM Systems

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2012年第24期30卷 3902-3910页

作者： Gao, Ying Ke, Jian Hong Zhong, Kang Ping Cartledge, John C. Yam, Scott S. -H. Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada

For 112 Gb/s dual-polarization 16-ary quadrature amplitude modulation systems, the performance and complexity of the low-pass filter (LPF)-assisted digital back-propagation (DBP) algorithm for mitigating intrachannel fiber nonlinearity are investigated. Comparison is made with both linear equalization and the standard DBP algorithm for single-channel transmission (simulation and experiment) and for wavelength division multiplexed (WDM) transmission with channel spacings of 50 and 35 GHz (simulation). With optimized values for the algorithm parameters, the simulation results show that, compared to linear equalization, the 0.2 steps/span LPF-assisted DBP algorithm can increase the transmission distance by 84%, 40%, and 17% for a single-channel, 50 GHz channel-spaced WDM, and 35 GHz channel-spaced WDM transmission, respectively. These improvements in the transmission distance are 54%, 75%, and 77% of those achieved with the 4 steps/span standard DBP algorithm but at considerably lower complexity. Single-channel experimental results show that the 0.25 steps/span LPF-assisted DBP algorithm can increase the transmission distance by 43%, which is 68% of the improvement achieved with the 4 steps/span standard DBP algorithm. Compared to the standard DBP algorithm, the LPF-assisted DBP algorithm can allow a reduction in the number of steps/span, but with an increased computational complexity for each step. The two DBP algorithms are compared in terms of the number of real multiplications per bit, thus allowing the algorithm with lower complexity to be determined at a given level of performance.

关键词： Digital back propagation dual-polarization 16-ary quadrature amplitude modulation split-step fourier algorithm wavelength division multiplexing

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Performance Comparison of Various PSK Modulation Schemes for Ultra-High Speed Long-Haul Fiber-Optic Communication System

Performance Comparison of Various PSK Modulation Schemes for...

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IEEE International Conference on Advanced Networks and Telecommunciations Systems (ANTS)

作者： Faisal, Mohammad Rahman, Md. Hasan Bangladesh Univ Engn & Technol Dept Elect & Elect Engn Dhaka Bangladesh

ISBN: (纸本)9781467351324;9781467351300

In this paper, the performance of differential phase modulation schemes for ultra-high speed long-haul fiber-optic communication system has been evaluated and compared. The quality factor Q is measured from the eye-pattern at the end of the dispersion-managed transmission line. Only self-phase modulation, dispersion effect and amplifier noise are considered here.

关键词： PSK Q-factor Self-Phase Modulation split-step fourier algorithm

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The analysis of parabolic equation model solutions using split-step/finite difference method 23

The analysis of parabolic equation model solutions using spl...

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23rd International Congress on Acoustics: Integrating 4th EAA Euroregio, ICA 2019

作者： Aslan, Mustafa

ISBN: (纸本)9783939296157

Parabolic equation models solved using the split-step fourier (SSF) algorithm is commonly studied for the modeling of wave propagation in the underwater environment. The smoothing function, in the solution of realistic problems, is introduced in the SSF algorithm to treat the density change between the water column and the sediment layer. The algorithm with the smoothing approach accumulates the phase error with the range. As an alternative method, by Yevick and Thomson, the hybrid split-step/finite difference method was developed to accomplish the density discontinuity issue numerically, and it significantly improved the phase error. The additional operator containing density dependent terms are introduced to implement the hybrid approach in this method. The results of the SSF parabolic equation model with the smoothing approach and with the hybrid approach are compared and discussed to see the effect of numerical parameters on the model implementation in this research. © 2019 Proceedings of the International Congress on Acoustics. All rights reserved.

关键词： Density discontinuity Parabolic equation Smoothing function split-step fourier algorithm split-step/finite difference method

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Higher-order boundary and rough surface treatment of the MMPE model in the evaluation of scattering effects

Higher-order boundary and rough surface treatment of the MMP...

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作者： Tan, Yi Ling Naval Postgraduate School

学位级别：硕士

This research aims to improve the Monterey-Miami Parabolic Equation model (MMPE) by incorporating a higher-order hybrid boundary treatment and Fred D. Tappert’s field transformational model to add surface scattering to the existing models. The impact of these two additions is investigated for improvements in accuracy and stability to the current MMPE model under rough surface conditions. Both models were treated with a Pierson-Moskowitz rough surface spectrum. It was hoped that the hybrid model would provide a reduction of the phase errors inherent to the MMPE at long range; however, no improvements were seen, and the sensitivity to depth mesh size was not reduced. This could be the result of errors in the derivation of the higher-order algorithm. The transformational model used Tappert’s field transformation to incorporate surface scattering and is thought to perform better when compared with the hybrid model by capturing higher modes of propagation. The inclusion of rough surface scattering in both models was evaluated for energy transmission across the air/water interface and beam dispersion. It was observed that the rough surface had minimal impact on energy transmission.

关键词： Acoustic propagation rough sea surface scattering acoustic scattering split-step fourier algorithm finite difference algorithm

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Simulation Analysis of the Radar Detection Ability in the Multilayer duct Environment

Simulation Analysis of the Radar Detection Ability in the Mu...

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2009通信理论与技术新发展——第十四届全国青年通信学术会议

作者： DING Ju-li~1 FEI Jian-fang~1 HU Xiao-hua~2 ZHOU Xin~(1,3) (1 Institution of Meteorology,PLA Univ.of Sci.& Tech.,Nanjing 211101,China 2 61741 Unit, Beijing 100081,China 3 91404 Unit,Qinhuangdao 066200,China)

The anomalous EM propagation characteristics and the radar detection ability in the multilayer duct environment are analyzed through simulation methods based on the parabolic equation model and split-step fourier algorithm *** conclusions are as follows:Electromagnetic waves in the atmospheric duct environment may result in the phenomena of enhanced propagation,radar hole and skip zones;the influence is more remarkable when the antenna is located just in the duct and the propagation loss of the trapped wave is very small in the duct *** detection is seldom influenced by the duct which lies far above the radar,but the impact is more significant when the duct layer just cover or lies below the radar;besides that,the type,strength and thickness of the duct also affect and restrict the extent of the influence.

关键词： atmospheric duct parabolic equation model split-step fourier algorithm anomalous propagation

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Performance Comparison of Various PSK Modulation Schemes for Ultra-High Speed Long-Haul Fiber-Optic Communication System

Performance Comparison of Various PSK Modulation Schemes for...

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IEEE International Symposium on Advanced Networks and Telecommunications Systems

作者： Mohammad Faisal Md. Hasan Rahman Department of Electrical & Electronic Engineering Bangladesh University of Engineering and Technology

ISBN: (纸本)9781467351300

关键词： PSK G-factor Self-Phase Modulation split-step fourier algorithm

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