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Träfflista för sökning "WFRF:(Karlsson Magnus 1967 ) "

Sökning: WFRF:(Karlsson Magnus 1967 )

  • Resultat 61-70 av 555
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61.
  • Bakhshi, Bamdad, 1970, et al. (författare)
  • Measurement of the differential group delay in installed optical fibers using polarization multiplexed solitons
  • 1999
  • Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 11:5, s. 593-595
  • Tidskriftsartikel (refereegranskat)abstract
    • We experimentally demonstrate a new technique for measurement of the differential group delay (DGD) in optical fibers using polarization-division multiplexed (PDM) solitons: the change in the separation of orthogonally polarized solitons propagating along different principal axes in a fiber equals the DGD at the signal wavelength. Based on this principle, we use PDM solitons to measure the accumulated DGD at different distances along a 400-km installed fiber. The measured DGD exhibits the expected square-root-of-length dependence, corresponding to a polarization-mode dispersion of 0.26 ps/km1/2. The results are in excellent agreement with those obtained by a commercial instrument utilizing Jones matrix eigenanalysis.
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62.
  • Bakhshi, Bamdad, 1970, et al. (författare)
  • Soliton interaction penalty reduction by receiver filtering
  • 1998
  • Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 10:7, s. 1042-1044
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first detailed numerical study of the impact of receiver low-pass filtering in soliton interaction-limited communication systems. We propagate 40-Gb/s pseudorandom bit sequences (PRBS's) of 28-1 solitons up to one soliton collision distance (Zc-) and optimize the filter bandwidth to minimize the interaction induced eye opening penalty. The distance at 0.5-dB penalty is increased over 40% through filtering. The penalty is essentially pulsewidth independent when considering distances normalized by Zc. We also show that PRBS's of at least 28 - 1 solitons are required to accurately simulate random data.
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63.
  • Beygi, Lotfollah, 1977, et al. (författare)
  • A Discrete-Time Model for Uncompensated Single-Channel Fiber-Optical Links
  • 2012
  • Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 60:11, s. 3440-3450
  • Tidskriftsartikel (refereegranskat)abstract
    • An analytical discrete-time model is introduced for single-wavelength polarization multiplexed nonlinear fiber-optical channels based on the symmetrized split-step Fourier method (SSFM). According to this model, for high enough symbol rates, a fiber-optic link can be described as a linear dispersive channel with additive white Gaussian noise (AWGN) and a complex scaling. The variance of this AWGN noise and the attenuation are computed analytically as a function of input power and channel parameters. The results illustrate a cubic growth of the noise variance with input power. Moreover, the cross effect between the two polarizations and the interaction of amplifier noise and the transmitted signal due to the nonlinear Kerr effect are described. In particular, it is found that the channel noise variance in one polarization is affected twice as much by the transmitted power in that polarization than by the transmitted power in the orthogonal polarization.The effect of pulse shaping is also investigated through numerical simulations. Finally, it is shown that the analytical performance results based on the new model are in close agreement with numerical results obtained using the SSFM for a symbol rate of 28 Gbaud and above.
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64.
  • Beygi, Lotfollah, 1977, et al. (författare)
  • A novel multilevel coded modulation scheme for fiber optical channel with nonlinear phase noise
  • 2010
  • Ingår i: Proc. Global Communications Conference, Miami, FL. - 9781424456383
  • Konferensbidrag (refereegranskat)abstract
    • A multilevel coded modulation (MLCM) system in the presence of nonlinear phase noise for fiber optical communication is introduced. The proposed scheme exploits a 16-point ring constellation with nonlinear post compensation of the self phase modulation produced via the Kerr effect. A new set partitioning based on the Ungerboeck approach is introduced to maintain unequal error protection in amplitude and phase direction. The rate allocation for the MLCM component codes for different fiber lengths and transmit powers are done numerically. Simulation results show that the proposed MLCM system provides up to 2 dB gain over a forward error correcting scheme for a block error rates around 10-9, with the same overhead (7%) and complexity. ©2010 IEEE.
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65.
  • Beygi, Lotfollah, 1977, et al. (författare)
  • A novel rate allocation method for multilevel coded modulation
  • 2010
  • Ingår i: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. - 9781424469604 ; , s. 1983-1987
  • Konferensbidrag (refereegranskat)abstract
    • We present a new rate allocation scheme for multilevelcoded modulation based on the minimization of the totalblock error rate (BLER). The proposed method uses affine codecomponents and hard decision multistage decoding. Exhaustivesearch for the rate allocation which minimizes the total BLERjustifies the near-optimum performance of the introduced methodin moderate to high SNRs. Compared to previous approaches thisnew rate allocation scheme can improve the performance of thesystem by 1 dB at BLER = 10−6 for 16-QAM with Ungerboeck setpartitioning. Interestingly, our results indicate that the optimumrate allocation is a function of the SNR. Finally, the performanceof some specific codes are evaluated by simulation and unionbounds to verify the theoretical results.
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66.
  • Beygi, Lotfollah, 1977, et al. (författare)
  • Adaptive Coded Modulation for Nonlinear Fiber-Optical Channels
  • 2012
  • Ingår i: 2012 IEEE Globecom Workshops, Anaheim, USA, 3-7 December 2012. - 9781467349420 ; , s. 331-335
  • Konferensbidrag (refereegranskat)abstract
    • A low complexity hybrid polar low-density parity check (LDPC) coded modulation (CM) scheme is introduced for a single-wavelength fiber-optical channel. In the proposed scheme, we exploit a low complexity probabilistic shaping together with a four-dimensional (4D) mapping to reduce the complexity of a 4D non-binary LDPC CM scheme for fiber-optic channels. The proposed scheme has a flexible structure and it can be used as an adaptive-rate CM scheme. The numerical results show that the forward error correction (FEC) threshold of the introduced CM scheme can be significantly improved by probabilistic shaping with a negligible increase in the system complexity. In particular, the FEC threshold for the uncoded symbol error rate of the introduced CM scheme with 4D 16-ary quadrature amplitude modulation can be improved from 0.058 to 0.072 by exploiting a shaping overhead (redundancy) of 0.016 for an information bit error rate of 10^{-5}.
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67.
  • Beygi, Lotfollah, 1977, et al. (författare)
  • Coded Modulation for Fiber-Optic Networks
  • 2014
  • Ingår i: IEEE Signal Processing Magazine. - 1558-0792 .- 1053-5888.
  • Tidskriftsartikel (refereegranskat)abstract
    • In this tutorial, we study the joint design of forward error correction and modulation for fiber-optic communications. To this end, we use an information-theoretic design framework to investigate coded modulation (CM) techniques for standard additive white Gaussian noise channels and fiber-optic channels. This design guideline helps us to provide a comprehensive overview of the CM schemes in the literature. Then, by invoking recent advances in optical channel modeling for non-dispersion-managed links, we discuss two- and four-dimensional CM schemes. Moreover, we discuss the electronic computational complexity and hardware constraints of CM schemes for optical communications. Finally, we address CM schemes with signal shaping and rate-adaptation capabilities to accommodate the data transmission scheme to optical links with different signal qualities.
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68.
  • Beygi, Lotfollah, 1977, et al. (författare)
  • On nonlinearly-induced noise in single-channel optical links with digital backpropagation
  • 2013
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 21:22, s. 26376-26386
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we investigate the performance limits of electronic chromatic dispersion compensation (EDC) and digital backpropagation (DBP) for a single-channel non-dispersion-managed fiber-optical link. A known analytical method to derive the performance of the system with EDC is extended to derive a first-order approximation for the performance of the system with DBP. In contrast to the cubic growth of the variance of the nonlinear noise-like interference, often called nonlinear noise, with input power for EDC, a quadratic growth is observed with DBP using this approximation. Finally, we provide numerical results to verify the accuracy of the proposed approach and compare it with existing analytical models.
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69.
  • Beygi, Lotfollah, 1977, et al. (författare)
  • On the dimensionality of multilevel coded modulation in the high SNR regime
  • 2010
  • Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 14:11, s. 1056-1058
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, the dimensionality of the multilevel coded modulation (MLCM) scheme is addressed. This study is done for an MLCM scheme with a N-dimensional (ND) constellation constructed from the Cartesian product of N identical 1D constellations in the high SNR regime. It is demonstrated that multidimensional MLCM with Reed--Solomon code components has better trade-off between coding gain and complexity than a 1D scheme. Specifically, a 4D MLCM system gains 1.4~dB over a 1D MLCM system with lower complexity at a block error of 10^{-6}. The gain increases to 2.5~dB asymptotically.
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70.
  • Beygi, Lotfollah, 1977, et al. (författare)
  • Optimization of 16-point Ring Constellations in the Presence of Nonlinear Phase Noise
  • 2011
  • Ingår i: Optical Fiber Communication Conference (OFC). - 2162-2701. - 9781557529060 ; , s. OThO4-
  • Konferensbidrag (refereegranskat)abstract
    • The optimum radius distribution in terms of the average symbol error rate (SER) for different 16-point signal sets is derived numerically for a fiber channel limited by nonlinear phase noise. The results show up to 2.4 dB performance improvement.
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  • Resultat 61-70 av 555
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