| 261. |
- Li, Shen, 1994, et al.
(författare)
-
Antialiased transmitter-side digital backpropagation
- 2020
-
Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 32:18, s. 1211-1214
-
Tidskriftsartikel (refereegranskat)abstract
- Digital backpropagation (DBP) is an electronic scheme for compensating nonlinear distortions in fiber transmission systems. Due to the nonlinearity-induced spectral broadening, the data must be oversampled to avoid aliasing, which increases the complexity and power consumption of the scheme. In this work, we show that aliasing can alternatively be prevented by distributed antialiasing filters, at a lower complexity. We proposed a new modified split-step Fourier method (SSFM) with easy-To-implement low-pass filters (LPFs) in the linear steps to avoid aliasing due to spectral broadening. Both the forward fiber propagation and a transmitter-side DBP are simulated using the modified SSFM. High-order modulation formats such as 256-Ary quadrature-Amplitude-modulation (256-QAM) and 1024-QAM transmissions at 28 Gbaud and 64 Gbaud over 1000 km fiber are considered, and our results show that the complexity of the DBP can be reduced by up to 50%. The optimal bandwidth of the LPFs is studied for both forward propagation and the DBP.
|
|
| 262. |
|
|
| 263. |
- Li, Shen, 1994, et al.
(författare)
-
Designing Voronoi Constellations to Minimize Bit Error Rate
- 2021
-
Ingår i: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. ; 2021-July, s. 1017-1022
-
Konferensbidrag (refereegranskat)abstract
- In a classical 1983 paper, Conway and Sloane presented fast encoding and decoding algorithms for a special case of Voronoi constellations (VCs), for which the shaping lattice is a scaled copy of the coding lattice. Feng generalized their encoding and decoding methods to arbitrary VCs. Less general algorithms were also proposed by Kurkoski and Ferdinand, respectively, for VCs with some constraints on their coding and shaping lattices. In this work, we design VCs with a cubic coding lattice based on Kurkoski's encoding and decoding algorithms. The designed VCs achieve up to 1.03 dB shaping gains with a lower complexity than Conway and Sloane's scaled VCs. To minimize the bit error rate (BER), pseudo-Gray labeling of constellation points is applied. In uncoded systems, the designed VCs reduce the required SNR by up to 1.1 dB at the same BER, compared with the same VCs using Feng's and Ferdinand's algorithms. In coded systems, the designed VCs are able to achieve lower BER than the scaled VCs at the same SNR. In addition, a Gray penalty estimation method for such VCs of very large size is introduced.
|
|
| 264. |
- Li, Shen, 1994, et al.
(författare)
-
Improved Simulation Accuracy of the Split-Step Fourier Method
- 2020
-
Ingår i: Optical Fiber Communication Conference. - 9781943580712
-
Konferensbidrag (refereegranskat)abstract
- We investigate a modified split-step Fourier method (SSFM) by including low-pass filters in the linear steps. This method can simultaneously achieve a higher simulation accuracy and a slightly reduced complexity.
|
|
| 265. |
- Li, Shen, 1994, et al.
(författare)
-
Low-Complexity Voronoi Shaping for the Gaussian Channel
- 2022
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 70:2, s. 865-873
-
Tidskriftsartikel (refereegranskat)abstract
- Voronoi constellations (VCs) are finite sets of vectors of a coding lattice enclosed by the translated Voronoi region of a shaping lattice, which is a sublattice of the coding lattice. In conventional VCs, the shaping lattice is a scaled-up version of the coding lattice. In this paper, we design low-complexity VCs with a cubic coding lattice of up to 32 dimensions, in which pseudo-Gray labeling is applied to minimize the bit error rate. The designed VCs have considerable shaping gains of up to 1.03 dB and finer choices of spectral efficiencies in practice compared with conventional VCs. A mutual information estimation method and a log-likelihood approximation method based on importance sampling for very large constellations are proposed and applied to the designed VCs. With error-control coding, the proposed VCs can have higher information rates than the conventional scaled VCs because of their inherently good pseudo-Gray labeling feature, with a lower decoding complexity.
|
|
| 266. |
- Li, Shen, 1994, et al.
(författare)
-
Power-Efficient Voronoi Constellations for Fiber-Optic Communication Systems
- 2023
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 41:5, s. 1298-1308
-
Tidskriftsartikel (refereegranskat)abstract
- Voronoi constellations (VCs) are considered as an effective geometric shaping method due to their high power efficiencies and low complexity. In this paper, the performance of 16- and 32-dimensional VCs with a variety of spectral efficiencies transmitted in the nonlinear fiber channel are investigated. Both single-channel and wavelength-division multiplexing systems are considered for the transmission of the VCs, as well as different signal processing schemes, including chromatic dispersion compensation and digital backpropagation. Multiple performance metrics including the uncoded bit error rate, mutual information (MI), and generalized mutual information (GMI) of VCs are evaluated. Compared with quadrature amplitude modulation (QAM) formats, the VCs provide 1.0--2.4 dB launch power gains, up to 0.50 bits/symbol/dimension-pair MI gains, up to around 30% potential reach increase at the same MI, and up to 0.30 bits/symbol/dimension-pair GMI gains in a limited launch power range. The observed performance gains over QAM are found higher than in the back-to-back case. Moreover, a general GMI estimation method for very large constellations using importance sampling is proposed for the first time.
|
|
| 267. |
- Lorences Riesgo, Abel, 1987, et al.
(författare)
-
Demonstration of Degenerate Vector Phase-Sensitive Amplification
- 2013
-
Ingår i: Optical Communication (ECOC 2013), 39th European Conference and Exhibition on. - : Institution of Engineering and Technology. - 9781849197595 ; 2013:622 CP, s. 492-494
-
Konferensbidrag (refereegranskat)abstract
- The performance of a degenerate vector (dual cross-polarized pump) phase-sensitive amplifier (PSA) is characterized and compared to a degenerate scalar (dual co-polarized pump) PSA. In both schemes, we assess the gain as a function of the signal state of polarization, verifying its compliance with theory, and the phase transfer function.
|
|
| 268. |
- Lorences Riesgo, Abel, 1987, et al.
(författare)
-
Experimental analysis of degenerate vector phase-sensitive amplification
- 2014
-
Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 22:18, s. 21889-21902
-
Tidskriftsartikel (refereegranskat)abstract
- We comprehensively investigate a degenerate vector phase-sensitive amplifier (PSA). We determine the gain dependence on the relative phase and polarization angle between the pumps and the degenerate signal wave. The vector PSA is experimentally shown to be sensitive to the pump states of polarization (SOP) due to polarization mode dispersion in the fiber. However, the scheme performance agrees well with theory under specific pump SOPs and we achieve an on-off gain over 10 dB with a small deviation from the theoretically expected results. In comparison to the scalar scheme, the proposed vector scheme has larger tolerance for pump depletion due to four-wave mixing between pumps and generation of higher-order idlers.
|
|
| 269. |
- Lorences Riesgo, Abel, 1987, et al.
(författare)
-
Frequency-Comb Regeneration for Self-Homodyne Superchannels
- 2016
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:8, s. 1800-1806
-
Tidskriftsartikel (refereegranskat)abstract
- We propose and demonstrate frequency-comb regeneration using injection locking and a parametric mixer. We theoretically evaluate the effect of the dispersive walk-off between the two unmodulated carriers from which the comb is regenerated. We calculate the maximum number of carriers which can be regenerated as a function of the laser linewidth and transmission distance when considering dispersion-unmanaged links. Experimentally, we demonstrate a 70 line comb generation without major linewidth degradation from two carriers with 15 dB optical signal-to-noise ratio (OSNR). The low OSNR operation is achieved by the use of optical injection locking. We also evaluate the degradation in the comb regeneration when the carriers are temporally decorrelated in order to emulate the effect of dispersive walk-off. When the temporal delay is 1.5 ns, the comb regeneration does not suffer from major degradation but when the delay is 10 ns, only 30 carriers can be regenerated without linewidth degradation, which agrees with our theoretical analysis.
|
|
| 270. |
- Lorences Riesgo, Abel, 1987, et al.
(författare)
-
Frequency-Comb Regeneration for Self-Homodyne Superchannels
- 2015
-
Ingår i: 41st European Conference on Optical Communication, ECOC 2015, Valencia, Spain, 27 September - 1 October 2015. - 9788460817413 ; 2015-November, s. paper We.3.6.2-
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate frequency-comb regeneration from two received unmodulated carriers usinga parametric mixer. For 10 dB optical signal-to-noise ratio of the unmodulated carriers, up to 60 carriersare generated without linewidth degradation.
|
|
