| 1. |
- Agrell, Erik, 1965, et al.
(författare)
-
Influence of Behavioral Models on Multiuser Channel Capacity
- 2015
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:17, s. 3507-3515
-
Tidskriftsartikel (refereegranskat)abstract
- In order to characterize the channel capacity of a wavelength channel in a wavelength-division multiplexed (WDM) system, statistical models are needed for the transmitted signals on the other wavelengths. For example, one could assume that the transmitters for all wavelengths are configured independently of each other, that they use the same signal power, or that they use the same modulation format. In this paper, it is shown that these so-called behavioral models have a profound impact on the single-wavelength achievable information rate. This is demonstrated by establishing, for the first time, upper and lower bounds on the maximum achievable rate under various behavioral models, for a rudimentary WDM channel model.
|
|
| 2. |
- Alfredsson, Arni, 1989, et al.
(författare)
-
Joint-Polarization Phase-Noise Estimation and Symbol Detection for Optical Coherent Receivers
- 2016
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:18, s. 4394-4405
-
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.
|
|
| 3. |
|
|
| 4. |
- Alvarado, Alex, 1982, et al.
(författare)
-
Four-Dimensional Coded Modulation with Bit-Wise Decoders for Future Optical Communications
- 2015
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:10, s. 1993-2003
-
Tidskriftsartikel (refereegranskat)abstract
- Coded modulation (CM) is the combination of forward error correction (FEC) and multilevel constellations. Coherent optical communication systems result in a four-dimensional (4D) signal space, which naturally leads to 4D-CM transceivers. A practically attractive design paradigm is to use a bit-wise decoder, where the detection process is (suboptimally) separated into two steps: soft-decision demapping followed by binary decoding. In this paper, bit-wise decoders are studied from an information-theoretic viewpoint. 4D constellations with up to 4096 constellation points are considered. Metrics to predict the post-FEC bit-error rate (BER) of bit-wise decoders are analyzed. The mutual information is shown to fail at predicting the post-FEC BER of bit-wise decoders and the so-called generalized mutual information is shown to be a much more robust metric. For the suboptimal scheme under consideration, it is also shown that constellations that transmit and receive information in each polarization and quadrature independently (e.g., PM-QPSK, PM-16QAM, and PM-64QAM) outperform the best 4D constellations designed for uncoded transmission. Theoretical gains are as high as 4 dB, which are then validated via numerical simulations of low-density parity check codes.
|
|
| 5. |
- Alvarado, A., et al.
(författare)
-
Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems
- 2016
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:2, s. 707-721
-
Tidskriftsartikel (refereegranskat)abstract
- The FEC limit paradigm is the prevalent practice for designing optical communication systems to attain a certain bit error rate (BER) without forward error correction (FEC). This practice assumes that there is an FEC code that will reduce the BER after decoding to the desired level. In this paper, we challenge this practice and show that the concept of a channel-independent FEC limit is invalid for soft-decision bit-wise decoding. It is shown that for low code rates and high-order modulation formats, the use of the soft-decision FEC limit paradigm can underestimate the spectral efficiencies by up to 20%. A better predictor for the BER after decoding is the generalized mutual information, which is shown to give consistent post-FEC BER predictions across different channel conditions and modulation formats. Extensive optical full-field simulations and experiments are carried out in both the linear and nonlinear transmission regimes to confirm the theoretical analysis.
|
|
| 6. |
- Alvarado, A., et al.
(författare)
-
Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems
- 2015
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:20, s. 4338-4352
-
Tidskriftsartikel (refereegranskat)abstract
- The FEC limit paradigm is the prevalent practice for designing optical communication systems to attain a certain bit error rate (BER) without forward error correction (FEC). This practice assumes that there is an FEC code that will reduce the BER after decoding to the desired level. In this paper, we challenge this practice and show that the concept of a channel-independent FEC limit is invalid for soft-decision bit-wise decoding. It is shown that for low code rates and high-order modulation formats, the use of the soft-decision FEC limit paradigm can underestimate the spectral efficiencies by up to 20%. A better predictor for the BER after decoding is the generalized mutual information, which is shown to give consistent post-FEC BER predictions across different channel conditions and modulation formats. Extensive optical full-field simulations and experiments are carried out in both the linear and nonlinear transmission regimes to confirm the theoretical analysis.
|
|
| 7. |
|
|
| 8. |
- Bamiedakis, N., et al.
(författare)
-
40 Gb/s Data Transmission Over a 1-m-Long Multimode Polymer Spiral Waveguide for Board-Level Optical Interconnects
- 2015
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:4, s. 882-888
-
Tidskriftsartikel (refereegranskat)abstract
- Optical interconnects have attracted considerable attention for use in short-reach communication links within high-performance electronic systems, such as data centers, supercomputers, and data storage systems. Multimode polymer waveguides, in particular, constitute an attractive technology for use in board-level interconnects as they can be cost-effectively integrated onto standard PCBs and allow system assembly with relaxed alignment tolerances. However, their highly multimoded nature raises important concerns about their bandwidth limitations and their potential to support very high on-board data rates. In this paper, we report record error-free (BER
|
|
| 9. |
- Bjork, G., et al.
(författare)
-
Proposed Implementation of "Non-Physical" Four-Dimensional Polarization Rotations
- 2016
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:14, s. 3317-3322
-
Tidskriftsartikel (refereegranskat)abstract
- Recently one of us proposed a new formalism for modeling electromagnetic wave transformations for coherent communication using a real, four-vector description instead of the conventionally used Jones calculus or the Mueller matrices. The four-vector can then handle all superpositions of two orthogonal polarization basis and two orthogonal time bases (e.g., the in-phase and quadrature phase). In developing this formulation it was found that to provide a general but minimal framework for such rotations, it is natural to divide the six generators of four-dimensional (4d) rotations into two groups of three generators, the right-and the left-isoclinic matrices. Of the six transformations these generators define, it was furthermore found that four of them are readily implemented by linear optical components, while two of then were impossible to implement by such means. In this paper, we detail the reason these two "unphysical" rotations cannot be implemented with linear optics. We also suggest how they can be implemented, but at a cost in the signal-to-noise ratio, and give this minimum cost.
|
|
| 10. |
- Björk, Gunnar, et al.
(författare)
-
Proposed Implementation of "Non-Physical" Four-Dimensional Polarization Rotations
- 2016
-
Ingår i: Journal of Lightwave Technology. - : IEEE. - 0733-8724 .- 1558-2213. ; 34:14, s. 3317-3322
-
Tidskriftsartikel (refereegranskat)abstract
- Recently one of us proposed a new formalism for modeling electromagnetic wave transformations for coherent communication using a real, four-vector description instead of the conventionally used Jones calculus or the Mueller matrices. The four-vector can then handle all superpositions of two orthogonal polarization basis and two orthogonal time bases (e.g., the in-phase and quadrature phase). In developing this formulation it was found that to provide a general but minimal framework for such rotations, it is natural to divide the six generators of four-dimensional (4d) rotations into two groups of three generators, the right-and the left-isoclinic matrices. Of the six transformations these generators define, it was furthermore found that four of them are readily implemented by linear optical components, while two of then were impossible to implement by such means. In this paper, we detail the reason these two "unphysical" rotations cannot be implemented with linear optics. We also suggest how they can be implemented, but at a cost in the signal-to-noise ratio, and give this minimum cost.
|
|
