| 211. |
- Karlsson, Magnus, 1967
(författare)
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Transmission systems with low noise phase sensitive parametric amplifiers
- 2015
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Ingår i: 41st European Conference on Optical Communication, ECOC 2015, Valencia, Spain, 27 September - 1 October 2015. - 9788460817413 ; 2015-November, s. Tu.3.2.1-
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Konferensbidrag (refereegranskat)abstract
- We review and present the recent research on phase-sensititve amplifiers, and describe how they can be used in transmission systems.
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| 212. |
- Karlsson, Magnus, 1967, et al.
(författare)
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Which is the most power-efficient modulation format in optical links?
- 2009
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 17:13, s. 10814-10819
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Tidskriftsartikel (refereegranskat)abstract
- By exploiting the electromagnetic wave's four-dimensional signal space, we find that for the additive white Gaussian noise channel, the modulation format with best sensitivity to be an 8-level format with 1.76 dB asymptotic gain over BPSK, for uncoded optical transmission with coherent detection. Low-complexity modulators are presented for the format, as well as an interpretation in terms of quantum-limited sensitivity.
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| 213. |
- Karout, Johnny, 1985, et al.
(författare)
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CMA Misconvergence in Coherent Optical Communication for Signals Generated from a Single PRBS
- 2011
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Ingår i: Wireless & optical communications conference, New Jersey, 15-16 April 2011. - 9781457704543
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Konferensbidrag (refereegranskat)abstract
- In the experimental study of modulators for coherent optical communications, it is common to generate multilevel signals using a single pseudo-random binary sequence. This simple experimental realization leads to symbol correlation. When modulators are studied in combination with adaptive receiver algorithms that rely on independent data, misconvergence may result. In this contribution, we investigate the impact of such correlation on a standard blind equalization method and provide guidelines to avoid misconvergence. Our results indicate that care needs to be taken when using a single PRBS sequence and that decorrelation delays must be chosen appropriately. We present simulation and theoretical results for 16-QAM, and show how our results can be applied to other multi-level constellations.
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| 214. |
- Karout, Johnny, 1985, et al.
(författare)
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Designing Power-Efficient Modulation Formats for Noncoherent Optical Systems
- 2011
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Ingår i: GLOBECOM - IEEE Global Telecommunications Conference. - 9781424492688
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Konferensbidrag (refereegranskat)abstract
- We optimize modulation formats for the additive white Gaussian noise channel with a nonnegative input constraint, also known as the intensity-modulated direct detection channel, with and without confining them to a lattice structure. Our optimization criteria are the average electrical and optical power. The nonnegativity input signal constraint is translated into a conical constraint in signal space, and modulation formats are designed by sphere packing inside this cone. Some remarkably dense packings are found, which yield more power-efficient modulation formats than previously known. For example, at a spectral efficiency of 1 bit/s/Hz, the obtained modulation format offers a 0.86 dB average electrical power gain and 0.43 dB average optical power gain over the previously best known modulation formats to achieve a symbol error rate of 10^-6. This modulation turns out to have a lattice-based structure. At a spectral efficiency of 3/2 bits/s/Hz and to achieve a symbol error rate of 10^-6, the modulation format obtained for optimizing the average electrical power offers a 0.58 dB average electrical power gain over the best lattice-based modulation and 2.55 dB gain over the best previously known format. However, the modulation format optimized for average optical power offers a 0.46 dB average optical power gain over the best lattice-based modulation and 1.35 dB gain over the best previously known format.
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| 215. |
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| 216. |
- Karout, Johnny, 1985, et al.
(författare)
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Optimizing Constellations for Single-Subcarrier Intensity-Modulated Optical Systems
- 2012
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Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 58:7, s. 4645-4659
-
Tidskriftsartikel (refereegranskat)abstract
- We optimize modulation formats for the additive white Gaussian noise channel with nonnegative input, also known as the intensity-modulated direct-detection channel, with and without confining them to a lattice structure. Our optimization criteria are the average electrical, average optical, and peak power. The nonnegative constraint on the input to the channel is translated into a conical constraint in signal space, and modulation formats are designed by sphere packing inside this cone. Some dense packings are found, which yield more power-efficient modulation formats than previously known. For example, at a spectral efficiency of 1.5 bit/s/Hz, the modulation format optimized for average electrical power has a 2.55 dB average electrical power gain over the best known format to achieve a symbol error rate of 10-6 . The corresponding gains for formats optimized for average and peak optical power are 1.35 and 1.72 dB, respectively. Using modulation formats optimized for peak power in average-power limited systems results in a smaller power penalty than when using formats optimized for average power in peak-power limited systems. We also evaluate the modulation formats in terms of their mutual information to predict their performance in the presence of capacity-achieving error-correcting codes, and finally show numerically and analytically that the optimal modulation formats for reliable transmission in the wideband regime have only one nonzero point.
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| 217. |
- Karout, Johnny, 1985, et al.
(författare)
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Power efficient subcarrier modulation for intensity modulated channels
- 2010
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 18:17, s. 17913-17921
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Tidskriftsartikel (refereegranskat)abstract
- We compare formats for optical intensity modulation limited by thermal noise with the assumption of having ideal devices. At the same bitrate and bandwidth, a hitherto unknown format turns out to be more power efficient than known formats. This new modulation, which is a hybrid between on-off keying and phase-shift keying, belongs to the subcarrier modulation family. At asymptotically high signal-to-noise ratios, this hybrid scheme has a 1.2 dB average electrical power gain and 0.6 dB average optical power gain compared to OOK, while it has a 3.0 dB average electrical power gain and 2.1 dB average optical power gain compared to subcarrier QPSK.
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| 218. |
- Keykhosravi, Kamran, 1990, et al.
(författare)
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When to Use Optical Amplification in Noncoherent Transmission: An Information-Theoretic Approach
- 2020
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 68:4, s. 2438-2445
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Tidskriftsartikel (refereegranskat)abstract
- The standard solution for short-haul fiber-optic communications is to deploy noncoherent systems, i.e., to modulate and detect only the light intensity. In such systems, the signal is corrupted with optical noise from amplifiers and with thermal (electrical) noise. The capacity of noncoherent optical links has been studied extensively in the presence of either optical noise or thermal noise. In this paper, for the first time, we characterize the capacity under an average power constraint with both noise sources by establishing upper and lower bounds. In the two extreme cases of zero optical noise or zero thermal noise, we assess our bounds against some well-known results in the literature; improvements in both cases are observed. Next, for amplified fiber-optic systems, we study the trade-off between boosting signal energy (mitigating the effects of thermal noise) and adding optical noise. For a wide spectrum of system parameters and received power levels, we determine the optimal amplification gain. While mostly either no amplification or high-gain amplification is optimal, the best performance is for some parameter intervals achieved at finite gains.
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| 219. |
- Khan, Fahd Ahmed, 1984, et al.
(författare)
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Electronic dispersion compensation by Hadamard transformation
- 2010
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Ingår i: Optical Fiber Communication Conference (OFC) - Proceedings. - Washington, D.C. : OSA. - 9781557528841 ; , s. paper OWV4-
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Konferensbidrag (refereegranskat)abstract
- We demonstrate that the Hadamard transform can be applied to look up table (LUT)-based predistorters to simultaneously compress and optimize the LUT for dispersion-limited links.
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| 220. |
- Kolltveit, Erling, et al.
(författare)
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Single-wavelength 40 Gbit/s soliton field transmission experiment over 400 km of installed fibre
- 1999
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 35:1, s. 75-76
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Tidskriftsartikel (refereegranskat)abstract
- 40Gbit/s soliton transmission over 400km (57km amplifier spacing) of installed lines without in-line control has been achieved. The maximum transmission penalties for parallel polarised and polarisation division multiplexed soliton transmission were ∼4 and 1dB, respectively. The transmission distance is the longest ever reported for a field trial with a single wavelength bit rate > 20Gbit/s for any optical transmission format. The polarisation mode dispersion was numerically found to completely dominate the system performance.
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