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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Blösch, Günter, et al.
(författare)
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Twenty-three unsolved problems in hydrology (UPH) - a community perspective
- 2019
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 64:10, s. 1141-1158
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Tidskriftsartikel (refereegranskat)abstract
- This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.
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| 4. |
- Kerrebrouck, Joris Van, et al.
(författare)
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High-speed PAM4-based Optical SDM Interconnects with Directly Modulated Long-wavelength VCSEL
- 2019
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Ingår i: Journal of Lightwave Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8724 .- 1558-2213. ; 37:2, s. 356-362
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the demonstration of high-speed PAM-4 transmission using a 1.5-μm single-mode vertical cavity surface emitting laser (SM-VCSEL) over multicore fiber with 7 cores over different distances. We have successfully generated up to 70 Gbaud 4-level pulse amplitude modulation (PAM-4) signals with a VCSEL in optical back-to-back, and transmitted 50 Gbaud PAM-4 signals over both 1-km dispersion-uncompensated and 10-km dispersion-compensated in each core, enabling a total data throughput of 700 Gbps over the 7-core fiber. Moreover, 56 Gbaud PAM-4 over 1-km has also been shown, whereby unfortunately not all cores provide the required 3.8 × 10$^-3$bit error rate (BER) for the 7% overhead-hard decision forward error correction (7% OH HDFEC). The limited bandwidth of the VCSEL and the adverse chromatic dispersion of the fiber are suppressed with pre-equalization based on accurate end-to-end channel characterizations. With a digital post-equalization, BER performance below the 7% OH-HDFEC limit is achieved over all cores. The demonstrated results show a great potential to realize high-capacity and compact short-reach optical interconnects for data centers.
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| 6. |
- Zhang, Lu, et al.
(författare)
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Kernel mapping for mitigating nonlinear impairments in optical short-reach communications
- 2019
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Ingår i: Optics Express. - : OSA - The Optical Society. - 1094-4087. ; 27:21, s. 29567-29580
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear impairments induced by the opto-electronic components are one of the fundamental performance-limiting factors in high-speed optical short-reach communications, significantly hindering capacity improvement. This paper proposes to employ a kernel mapping function to map the signals in a Hilbert space to its inner product in a reproducing kernel Hilbert space, which has been successfully demonstrated to mitigate nonlinear impairments in optical short-reach communication systems. The operation principle is derived. An intensity modulation/direct detection system with 1.5-µm vertical cavity surface emitting laser and 10-km 7-core fiber achieving 540.68-Gbps (net-rate 505.31-Gbps) has been carried out. The experimental results reveal that the kernel mapping based schemes are able to realize comparable transmission performance as the Volterra filtering scheme even with a high order.
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| 7. |
- Zhang, Lu, et al.
(författare)
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Nonlinearity Tolerant High-speed DMT Transmission with 1.5-μm Single-mode VCSEL and Multi-core Fibers for Optical Interconnects
- 2019
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Ingår i: Journal of Lightwave Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8724 .- 1558-2213. ; 37:2, s. 380-388
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally demonstrate the generation of 107-Gbit/s net-rate optical discrete multitone (DMT) signal using a 1.5-μm single-mode vertical cavity surface emitting laser (VCSEL) with modulation bandwidth of 22-GHz. Utilizing a nonlinearity-tolerant channel equalization algorithm for digital signal processing (DSP), total net-rates of 726.6-Gbit/s over 2.5-km dispersion-uncompensated 7-core fiber and 533.1-Gbit/s over 10-km dispersion-compensated 7-core fiber below 7% overhead hard-decision forward error correction (HD-FEC) limit have been experimentally achieved with a 1.5-μm VCSEL based intensity-modulation direct-detection (IM/DD) system. The features of the 1.5-μm single-mode VCSEL, 2.5-km/10km multi-core fibers and fan-in/fan-out modules are presented. Besides, the Volterra series based nonlinearity-tolerant channel equalization algorithm, which improves the signal-to-noise ratio (SNR) with more than 5-dB, is mathematically described and experimentally validated. The results have demonstrated that 1.5-μm single-mode VCSEL and multi-core fiber based transmission can be a promising candidate to solve the capacity challenges in short-reach optical interconnects.
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| 8. |
- Zhang, Lu, et al.
(författare)
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Toward terabit digital radio over fiber systems : Architecture and key technologies
- 2019
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Ingår i: IEEE Communications Magazine. - : Institute of Electrical and Electronics Engineers Inc.. - 0163-6804 .- 1558-1896. ; 57:4, s. 131-137
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Tidskriftsartikel (refereegranskat)abstract
- To support massive deployment of broadband radio applications, such as 5G and high-definition videos for terrestrial televisions, large system capacity and high spectrum efficiency are highly demanded in radio over fiber (RoF) systems. In this article, we propose a terabit digital RoF system capable of providing high-speed transmission, where multicore fiber (MCF) is introduced for the access segment between the central unit and remote unit. Two key technologies that greatly enhance system capacity and spectrum efficiency, namely MCF enabled self-homodyne detection and compressed quantization, are demonstrated.
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