| 121. |
- Kallstenius, T, et al.
(författare)
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On the degradation of InGaAsP/InP-based bulk lasers
- 1999
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Ingår i: JOURNAL OF LIGHTWAVE TECHNOLOGY. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8724. ; 17:12, s. 2584-2594
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Tidskriftsartikel (refereegranskat)abstract
- Degradation of InGaAsP/InP-based buried-heterostructure bulk (BH-bulk) lasers has been studied by means of electroluminescence (EL), photoluminescence (PL), electron-beam-induced current (EBIC) and transmission electron microscopy (TEM). Lasers with p/n a
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| 122. |
- Karlsson, Magnus, 1967, et al.
(författare)
-
Effects of Nonlinearities on PMD-Induced System Impairments
- 2006
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 24:11, s. 4127-4137
-
Tidskriftsartikel (refereegranskat)abstract
- It is well known that cross-phase-modulation-induced polarization rotation, cross-polarization modulation (XPolM), significantly degrades the performance of polarization-mode-dispersion (PMD) compensators. In this paper, the research on XPolM is reviewed, unique simulations of XPolM in the presence of walk off are presented, and some pitfalls are demonstrated with respect to choice of data streams in such simulations. Then, the authors discuss how XPolM affects PMD and PMD-induced outage probabilities (OP) in fiber-communication systems by providing analytical formulas for the OP with and without XPolM. Finally, the XPolM and PMD compensation are tied together by giving simple rules of thumb for when XPolM degrades PMD compensated systems, and PMD mitigation methods that are robust to XPolM are discussed.
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| 123. |
- Karlsson, Magnus, 1967
(författare)
-
Four-dimensional Rotations in Coherent Optical Communications
- 2014
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 32:6, s. 1246-1257
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Tidskriftsartikel (refereegranskat)abstract
- To model electromagnetic wave propagation for coherent communications without polarization dependent losses, the unitary 2 x 2 Jones transfer matrix formalism is typically used. In this study, we propose an alternative formalism to describe such transformations based on rotations in four-dimensional (4d) Euclidean space. This formalism is usually more attractive from a communication theoretical perspective, since decisions and symbol errors can be related to geometric concepts such as Euclidean distances between points and decision boundaries. Since 4d rotations is a richer description than the conventional Jones calculus, having six rather than four degrees of freedom (DOF), we propose an extension of the Jones calculus to handle all six DOF. In addition, we show that the two extra DOF in the 4d description represents transformations that are nonphysical for propagating photons, since they does not obey the fundamental quantum mechanical boson commutation relations. Finally, we exemplify on how the nonphysical rotations can change the polarization-phase degeneracy of well-known constellations such as single-polarization QPSK, polarization-multiplexed (PM-) QPSK and polarization-switched (PS-) QPSK. For example, we show how PM-QPSK, which is well known to consist of four polarization states each having four-fold phase degeneracy, can be represented as eight states of polarizations, each with binary phase degeneracy.
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| 124. |
- Karlsson, Magnus, 1967
(författare)
-
Geometrical interpretation of second-order PMD
- 2006
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 24:1, s. 643 - 51
-
Tidskriftsartikel (refereegranskat)abstract
- A geometrical interpretation of second-order polarization mode dispersion (SOPMD) as the curved three-dimensional (3-D) area swept by the PMD vector as it increases with propagation in a birefringent system is introduced. The depolarization and polarization-dependent chromatic dispersion parts of the SOPMD can be viewed as projections of this area in orthogonal directions. This interpretation enables us to translate the problem of maximizing the SOPMD in, e.g., PMD emulators and programmable PMD sources to an isoperimetric problem, i.e., a problem of maximizing the area enclosed by a given perimeter, which has well-known solutions. Both the discrete problems corresponding to a set of birefringent wave plates are discussed, and the continuous problem in which an arbitrary birefringent medium is considered. Analytic formulas are derived for the first time for the maximum SOPMD, depolarization, and polarization-dependent chromatic dispersion that can be realized in PMD emulators
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| 125. |
- Karlsson, Magnus, 1967, et al.
(författare)
-
Long-term measurement of PMD and polarization drift in installed fibers
- 2000
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 18:7, s. 941-951
-
Tidskriftsartikel (refereegranskat)abstract
- We report the most detailed long-term measurement of polarization mode dispersion (PMD) made to date. We measured two separate fibers under the same time period, which makes it possible to compare the drift properties of two similar fibers in the same environment. The measured Jones matrices suffers from both random and systematic errors, a generic problem which we discuss in detail and solve. The results confirmed the well-known statistical properties of the PMD-vector. Furthermore, the drift averaged over wavelength is very well (96%) correlated between the two fibers. We finally quantified the temporal drift by computing the autocorrelation function of the PMD-vector analytically, both with respect to wavelength and to drift time. The analytical theory shows good agreement with the measurements.
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| 126. |
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| 127. |
- Karlsson, Magnus, 1967, et al.
(författare)
-
Multidimensional Modulation and Coding in Optical Transport [Invited]
- 2017
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 35:4, s. 876-884
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reviews the performance of optimized modulation formats in 2, 4, and 8 dimensions. We present performance (lower bounds) for higher dimensions by exploiting known performance of binary block codes. Ultimately, the achievable information rates of given modulation formats and receiver types are limited by the mutual information and generalized mutual information. We exemplify how these metrics can be used for system performance as well as to quantify the performance differences between four types of systems; using hard or soft decision on bits or symbols.
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| 128. |
- Karlsson, Magnus, 1967
(författare)
-
Probability density functions of the differential group delay in optical fiber communication systems
- 2001
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 19:3, s. 324-331
-
Tidskriftsartikel (refereegranskat)abstract
- Fiber communication systems limited by polarization-mode dispersion (PMD) are usually analyzed using statistics. The probability density function (pdf) of the differential group delay (DGD) is then crucial to know. There are cases for which the commonly used Maxwellian pdf is only approximate, e.g., PMD emulators, or systems with components having single components with large deterministic PMD. Those cases are discussed in this paper, and their pdfs are derived. To do this, we present a very general theory that allows for the derivation of the pdf for almost any birefringent transmission line. As a side result, we are able to prove that the square-sum concatenation formula is valid in almost every case of interest, even if the pdf is far from Maxwellian.
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| 129. |
- Karlsson, Magnus, 1967, et al.
(författare)
-
Quaternion approach to PMD and PDL phenomena in optical fiber systems
- 2004
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 22:4, s. 1137-1146
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we introduce the concept of quaternions (which is a generalization of the complex numbers) and quaternion calculus and demonstrate how this theory may be used to simplify the treatment of polarization phenomena in optical fibers. We apply quaternion calculus to two examples: 1) the description of polarization-dependent loss (PDL) elements and concatenation of such and 2) the description of pulse dynamics and broadening in transmission lines with both polarization-mode dispersion (PMD) and PDL. Finally we present some novel results from the investigation of pulse broadening in a simple system comprising a PMD element, followed by a perfect polarizer.
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| 130. |
- Karlsson, Magnus, 1967
(författare)
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Transmission Systems With Low Noise Phase-Sensitive Parametric Amplifiers
- 2016
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:5, s. 1411-1423
-
Tidskriftsartikel (refereegranskat)abstract
- This tutorial reviews the recent research on fiber-based phase-sensitive amplifiers (PSAs), and describes how they can be used in transmission systems. We describe the fundamentals of parametric amplifiers, their history, and their basic properties. Special emphasis is given to the noise properties and their implementation in transmission systems. The copier-PSA setup is described and compared to phase-insensitive links, and we describe the challenges in implementing these systems. Finally, we describe the polarization properties of vector PSAs, and the PSA use in compensation of nonlinear distortions.
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