| 61. |
- Alfredsson, Arni, 1989, et al.
(författare)
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Iterative Detection and Phase-Noise Compensation for Coded Multichannel Optical Transmission
- 2019
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 67:8, s. 5532-5543
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Tidskriftsartikel (refereegranskat)abstract
- The problem of phase-noise compensation for correlated phase noise in coded multichannel optical transmission is investigated. To that end, a simple multichannel phase-noise model is considered and the maximum a posteriori detector for this model is approximated using two frameworks, namely factor graphs (FGs) combined with the sum–product algorithm (SPA), and a variational Bayesian (VB) inference method. The resulting pilot-aided algorithms perform iterative phase-noise compensation in cooperation with a decoder, using extended Kalman smoothing to estimate the a posteriori phase-noise distribution jointly for all channels. The system model and the proposed algorithms are verified using experimental data obtained from space-division multiplexed multicore-fiber transmission. Through Monte Carlo simulations, the algorithms are further evaluated in terms of phase-noise tolerance for coded transmission. It is observed that they significantly outperform the conventional approach to phase-noise compensation in the optical literature. Moreover, the FG/SPA framework performs similarly or better than the VB framework in terms of phase-noise tolerance of the resulting algorithms, for a slightly higher computational complexity.
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| 62. |
- Alfredsson, Arni, 1989, et al.
(författare)
-
Joint Phase Tracking for Multicore Transmission with Correlated Phase Noise
- 2018
-
Ingår i: - 9781538653432 ; , s. 16-17
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Konferensbidrag (refereegranskat)abstract
- Space-division multiplexed transmission over multicore fibers offers potential for joint-core processing to compensate for correlated phase noise. We review methods that take advantage of the phase-noise correlation across cores and assess their benefits in terms of transmission reach and pilot-rate requirements.
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| 63. |
- Alfredsson, Arni, 1989, et al.
(författare)
-
Joint-Polarization Phase-Noise Estimation and Symbol Detection for Optical Coherent Receivers
- 2016
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:18, s. 4394-4405
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Tidskriftsartikel (refereegranskat)abstract
- The problem of optimal symbol detection in the presence of laser phase noise is studied, for uncoded polarization-multiplexed fiber-optic transmission. To this end, the maximum a posteriori (MAP) symbol detector is presented. Specifically, it is emphasized that obtaining phase-noise point estimates, and treating them as the true values of the phase noise, is in general suboptimal. Furthermore, a pilot-based algorithm that approximates the MAP symbol detector is developed, using approaches adopted from the wireless literature. The algorithm performs joint-polarization phase-noise estimation and symbol detection, for arbitrary modulation formats. Through Monte Carlo simulations, the algorithm is compared to existing solutions from the optical communications literature. It is demonstrated that joint-polarization processing can significantly improve upon the single-polarization case, with respect to linewidth tolerance. Finally, it is shown that with less than 3% pilot overhead, the algorithm can be used with lasers having up to 6 times larger linewidths than the most well-performing blind algorithms can tolerate.
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| 64. |
- Alfredsson, Arni, 1989, et al.
(författare)
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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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| 65. |
- 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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| 66. |
- 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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| 67. |
- Alfredsson, Arni, 1989, et al.
(författare)
-
Phase-Noise Compensation for Spatial-Division Multiplexed Transmission
- 2017
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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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| 68. |
- 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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| 69. |
- 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
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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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| 70. |
- 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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