Current Issue : July - September Volume : 2014 Issue Number : 3 Articles : 7 Articles
The dependence of the dynamic range of the phase generated carrier (PGC) technique on low-pass filters passbands is investigated\nusing a simulationmodel.Anonlinear character of this dependence,which could lead to dynamic range limitations ormeasurement\nuncertainty, is presented for the first time.Adetailed theoretical analysis is provided to verify the simulation results and these results\nare consistent with performed calculations. The method for the calculation of low-pass filters passbands according to the required\ndynamic range upper limit is proposed....
The size, shape, and location of unknown objects in the ground and in the body can be estimated by an electromagnetic imaging\ntechnique. An imaging approach to clear detection of two-dimensional geometries is proposed in this paper. Based on the inverse\nfinite-difference time-domain (FDTD) method, a phase interference technique using multidirectional pulses is employed. The\nadvantage of the proposed method is that it can clearly reconstruct the geometry in a simple calculation. Sample imaging results\nare demonstrated. The analysis of the FDTD results shows that the detectable object size is limited by the incident wavelength and\nthe measurement spacing and illustrates the detectability of multiple objects....
Effective density of vibrational states in H-bonded liquids was measured by Raman scatteringmethod. Actuality of a low-frequency\npart of the spectrum of the intermediate (fracton) region, which obeys a power law, indicates the correct application of the\npercolation model. The dependence of exponent on binary solutions concentration has been studied. Existence of correlation of\nthe fractal structure parameter and dynamic viscosity has been noted....
Accurate simulation from digital, submicron, optical elements is obtained by finite difference time domain (FDTD) results that\nare phase analyzed as sources for Huygens wavelets on fine scales much shorter than the wavelength used. Results, from the MIT\nelectromagnetic evaluation program, are renormalized by a method here called ââ?¬Å?refractive impulse.ââ?¬Â This is valid for polarized\nresponses from digital diffractive and focusing optics. The method is employed with plane wave incidence at any angle or with\ndiverging or converging beams. It is more systematic, more versatile, and more accurate than commercial substitutes....
This paper describes the state-of-the-art of polarization multiplexing for optical networks transmission. The use of polarization\ndivision multiplexing (PDM) permits to multiply the user capacity and increase the spectral efficiency. Combining PDM and\northogonal frequency division multiplexed (OFDM) modulation allows maximizing the optical transmission capacity. The\nexperimental demonstration of transmitting OFDM signals following ECMA-368 ultrawide band (UWB) standard in radio-overfiber\nusing PDM in passive optical networks is herein reported. The impact of cross-polarization and cochannel crosstalk is\nevaluated experimentally in a three-user OFDM-UWB subcarrier multiplexed (SCM) configuration per polarization. Each SCM\nuses up to three OFDM-UWB channels of 200Mbit/s each, achieving an aggregated bitrate of 1.2 Gbit/s with 0.76 bit/s/Hz spectral\nefficiency when using PDM transmission. The experimental results for the polarization-multiplexed SCM indicate that a 4 dB\nadditional polarization crosstalk interference can be expected compared to a nonpolarization-multiplexed transmission system\nwhich translates to 2.4 dB EVM penalty in the UWB signals. The successful PDM transmission of SCM multiuser OFDM-UWB\nover a passive optical network of 25 km standard-single mode fiber (SSMF) reach is demonstrated....
Theoretically, the characteristics matrix method is employed to investigate and compare the properties of the band gaps of the\none-dimensional ternary and binary lossy photonic crystals which are composed of double-negative and double-positive materials.\nThis study shows that by varying the angle of incidence, the band gaps for TM and TE waves behave differently in both ternary\nand binary lossy structures. The results demonstrate that, by increasing the angle of incidence for the TE wave, the width and the\ndepth of zero-??, zero-??, and Bragg gap increase in both ternary and binary structures. On the other hand, the enhancement of the\nangle of incidence for the TM wave contributes to reduction of the width and the depth of the zero-?? and Bragg gaps, and they\nfinally disappear for incidence angles greater than 50�° and 60�° for the binary structure and 40�° and 45�° for the ternary structures,\nrespectively. In addition, the details of the edges of the band gaps variations as a function of incidence angle for both structures are\nstudied....
This paper presents a fast and rigorous design method for grating-based metal-free polarizing filter applications using two-step\nhybrid optimization techniques. Grating structures utilizing the total internal reflection in a lamellar configuration were used\nto achieve metal-free solution, which is a key technology in the chirped pulse amplification for high power laser system. Here\ntwo polarizing filters were designed: polarization sensitive and polarization insensitive. Those polarization performances were\ncharacterized by the rigorous coupled-wave analysis (RCWA), and the design parameters of grating structures, pitch, depth, and\nfilling factor were optimized by two-step hybrid optimization procedure because the diffraction characteristics of grating-based\npolarizing filters are highly sensitive to small changes in design parameters. The Taguchi method is incorporated into selection\nprocess in the genetic algorithm, which indicates that the Taguchi method optimizes the design parameters in a coarsemanner, and\nthen, coarsely optimized parameters are finely optimized using the genetic algorithm. Therefore the proposed method could solve\nglobal numerical optimization problems with continuous variables. The proposed two-step hybrid optimization algorithm could\neffectively optimize the grating structures for the purpose of polarization filter applications, and the optimized grating structures\ncould selectively filter the incident light up to 99.8% as to TE or TM waves....
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