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

Sökning: WFRF:(Karlsson Magnus 1967 )

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41.
  • Akhmediev, N.N., et al. (författare)
  • Radiationless optical solitons with oscillating tails
  • 1994
  • Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018. ; 110:5-6, s. 540-544
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate, analytically and numerically, stationary soliton-like pulse propagation in nonlinear optical fibres, taking into account the effects of fourth order dispersion. A new type of stationary stable soliton-like solution is found. A unique feature of this type of solution is their unusual asymptotic behaviour (oscillating tails). © 1994.
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42.
  • Alfredsson, Arni, 1989, et al. (författare)
  • On the Impact of Intercore Skew on Joint-Core Carrier-Phase Estimation
  • 2019
  • Ingår i: European Conference on Optical Communication, ECOC. - : Institution of Engineering and Technology.
  • Konferensbidrag (refereegranskat)abstract
    • The impact of intercore skew on joint-core carrier-phase estimation in multicore-fiber transmission is studied. It is shown that the performance degradation is not dependent on the combined linewidth of the light-source laser and the local oscillator, but rather the ratio between the two linewidths.
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43.
  • Alfredsson, Arni, 1989, et al. (författare)
  • On the Performance of Joint-Core Carrier-Phase Estimation in the Presence of Intercore Skew
  • 2019
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 37:20, s. 5291-5298
  • Tidskriftsartikel (refereegranskat)abstract
    • The sharing of lasers in space-division multiplexed multicore-fiber transmission yields correlated phase noise across the spatial channels. As a result, system performance can be improved through the use of joint-core carrier-phase estimation (CPE). However, the presence of intercore skew can reduce the potential of such schemes. This paper studies the effects of skew on pilot-aided joint-core CPE, where via simulations, it is shown that joint-core processing can be made to perform similarly to or better than separate-core processing for any amount of skew. It is shown that for a given signal-to-noise ratio (SNR) and skew, the performance of joint-core CPE relative to separate-core CPE is highly dependent on the ratio of the light-source linewidth to the local oscillator (LO) linewidth. In general, the performance of joint-core CPE in the presence of skew improves as the LO linewidth decreases compared to the light-source laser linewidth, assuming that the spatial channels are digitally realigned at the receiver.
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44.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Optimization of Transmitter-Side Signal Rotations in the Presence of Laser Phase Noise
  • 2020
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 38:15, s. 3850-3858
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of transmitter-side multidimensional signal rotations on the performance of multichannel optical transmission are studied in the presence of laser phase noise. In particular, the laser phase noise is assumed to be uncorrelated between channels. To carry out this study, a simple multichannel laser-phase-noise model that has been experimentally validated for weakly-coupled multicore-fiber transmission is considered. As the considered rotation scheme is intended to work in conjunction with receiver-side carrier phase estimation (CPE), the model is modified to further assume that imperfect CPE has taken place, leaving residual phase noise in the processed signal. Based on this model, two receiver structures are derived and used to numerically optimize transmitter-side signal rotations through Monte Carlo simulations. For reasonable amounts of residual phase noise, rotations based on Hadamard matrices are found to be near-optimal for transmission of four-dimensional signals. Furthermore, Hadamard rotations can be performed for any dimension that is a power of two. By exploiting this property, an increase of up to 0.25 bit per complex symbol in an achievable information rate is observed for transmission of higher-order constellations.
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45.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Phase-Noise Compensation for Spatial-Division Multiplexed Transmission
  • 2017
  • Ingår i: Optics InfoBase Conference Papers. - 2162-2701.
  • Konferensbidrag (refereegranskat)abstract
    • The problem of correlated phase noise in spatial-division multiplexed transmission is studied. To compensate for the phase noise, an algorithm for joint-core phase-noise estimation and symbol detection is proposed, which outperforms conventional methods.
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46.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Pilot-Aided Joint-Channel Carrier-Phase Estimation in Space-Division Multiplexed Multicore Fiber Transmission
  • 2019
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 37:4, s. 1133-1142
  • Tidskriftsartikel (refereegranskat)abstract
    • The performance of pilot-aided joint-channel carrier-phase estimation (CPE) in space-division multiplexed multicore fiber (MCF) transmission with correlated phase noise is studied. To that end, a system model describing uncoded MCF transmission where the phase noise comprises a common laser phase noise, in addition to core- and polarization-specific phase drifts, is introduced. It is then shown that the system model can be regarded as a special case of a multidimensional random-walk phase-noise model. A pilot-aided CPE algorithm developed for this model is used to evaluate two strategies, namely joint-channel and per-channel CPE. To quantify the performance differences between the two strategies, their respective phase-noise tolerances are assessed through Monte Carlo simulations of uncoded transmission for different modulation formats, pilot overheads, laser linewidths, numbers of spatial channels, and degrees of phase-noise correlation across the channels. For 20 GBd transmission with 200 kHz combined laser linewidth and 1% pilot overhead, joint-channel CPE yields up to 3.4 dB improvement in power efficiency or 25.5% increased information rate. Moreover, through MCF transmission experiments, the system model is validated and the strategies are compared in terms of bit-error-rate performance versus transmission distance for uncoded transmission of different modulation formats. Up to 21% increase in transmission reach is observed for 1% pilot overhead through the use of joint-channel CPE.
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47.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Pilot Distributions for Joint-Channel Carrier-Phase Estimation in Multichannel Optical Communications
  • 2020
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 38:17, s. 4656-4663
  • Tidskriftsartikel (refereegranskat)abstract
    • Joint-channel carrier-phase estimation can improve the performance of multichannel optical communication systems. In the case of pilot-aided estimation, the pilots are distributed over a two-dimensional channel-time symbol block that is transmitted through multiple channels. However, suboptimal pilot distributions reduce the effectiveness of the carrier-phase estimation and thus result in unnecessary pilot overhead, which reduces the overall information rate of the system. It is shown that placing pilots identically in all channels is suboptimal in general. By instead optimizing the pilot distribution, the mean squared error of the phase-noise estimates can be decreased by over 90% in some cases. Moreover, it is shown that the achievable information rate can be increased by up to 0.05, 0.16, and 0.41 bits per complex symbol for dual-polarization 20 GBd transmission of 64-ary, 256-ary, and 1024-ary quadrature amplitude modulation over 20 four-dimensional channels, respectively, assuming a total laser linewidth of 200 kHz.
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48.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Pilot Distributions for Phase Tracking in Space-Division Multiplexed Systems
  • 2017
  • Ingår i: European Conference on Optical Communication, ECOC.
  • Konferensbidrag (refereegranskat)abstract
    • Several pilot distributions are compared for pilot-aided joint-core phase tracking in space-division multiplexed transmission affected by correlated phase noise. Results show that the best choice of distribution can reduce the bit error rate by a factor up to 170.
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49.
  • Alic, N., et al. (författare)
  • Benefits of Joint Statistics in MLSD-Equalized Transmission
  • 2009
  • Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 21:8, s. 495-497
  • Tidskriftsartikel (refereegranskat)abstract
    • We experimentally investigate and quantify performance improvement, accounting for multiple bit intervals' joint statistics in filtered equalized on-off keying OC-192 fiber-optic links relying on Viterbi-algorithm-based sequence detection. We demonstrate that the penalty associated with narrow filtering can be alleviated for the most part with an appropriate detection approach.
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50.
  • Alic, N., et al. (författare)
  • Joint Statistics and MLSD in Filtered Incoherent High-Speed Fiber-Optic Communications
  • 2010
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 28:10, s. 1564-1572
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, signal statistics and their utilization for detection in narrowly filtered equalized high-speed fiber-optic communications are investigated experimentally. Tradeoffs between log-likelihood metric applications and oversampling are covered in detail. It is, for the first time, demonstrated that performance loss in bandwidth-limited systems can be nearly fully recovered (to within 0.5 dB) by taking advantage of band-width-limitation-induced noise correlations and oversampling.
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