| 1. |
- Cornelissen, Johannes H C, et al.
(författare)
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Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
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| 2. |
- Eriksson, Tobias A., et al.
(författare)
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Crosstalk Impact on Continuous Variable Quantum Key Distribution in lticore Fiber Transmission
- 2019
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Ingår i: IEEE Photonics Technology Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1041-1135 .- 1941-0174. ; 31:6, s. 467-470
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the excess noise induced by crosstalk in a trench-assisted homogeneous 19-core fiber for a continuous variable quantum key distribution (CV-QKD) receiver. Crosstalk is studied for both 30 wavelength division multiplexing channels of 24.5-Gbaud PM-16QAM with 100-GHz channel spacing and for an amplified spontaneous emission signal with 37.5-GHz bandwidth. We show that in-band crosstalk from neighboring cores prohibits secret key generation. However, it is possible to place CV-QKD channels at wavelengths not used by the classical channels even though wideband amplified spontaneous emission noise is present. The excess noise induced by crosstalk from a neighboring core is shown to be time-dependent.
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| 3. |
- Eriksson, Tobias A., et al.
(författare)
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Wavelength Division Multiplexing of 194 Continuous Variable Quantum Key Distribution Channels
- 2020
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 38:8, s. 2214-2218
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the first continuous variable quantum key distribution (CV-QKD) system with fully digital phase and polarization tracking, enabling the first wavelength division multiplexing experiment for CV-QKD. We transmit 194 x 0.5 GHz channels with 25 GHz channel spacing, demonstrating an aggregate estimated asymptotic secret key rate of 172.6 Mbit/s over 25 km.
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| 4. |
- Lundberg, Lars, 1989, et al.
(författare)
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Master-slave carrier recovery for M-QAM multicore fiber transmission
- 2019
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 27:16, s. 22226-22236
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Tidskriftsartikel (refereegranskat)abstract
- Master-slave carrier recovery is a digital signal processing technique that uses correlated phase noise in multi-channel receivers to eliminate redundant carrier recovery blocks. In this paper we experimentally investigate the performance of master-slave carrier recovery for multicore fiber transmission in the presence of inter-channel nonlinear interference. Using a triple parallel loop setup we jointly receive three spatial channels in a 7-core fiber for transmission distances of up to 1600 km. We find that an increased launch power causes a moderate penalty on the slave channels. Furthermore, we study the penalty from a non-zero inter-core skew.
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| 5. |
- Okada, Tatsuaki, et al.
(författare)
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Thermal Infrared Imaging Experiments of C-Type Asteroid 162173 Ryugu on Hayabusa2
- 2017
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Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 208:1-4, s. 255-286
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Tidskriftsartikel (refereegranskat)abstract
- The thermal infrared imager TIR onboard Hayabusa2 has been developed to investigate thermo-physical properties of C-type, near-Earth asteroid 162173 Ryugu. TIR is one of the remote science instruments on Hayabusa2 designed to understand the nature of a volatile-rich solar system small body, but it also has significant mission objectives to provide information on surface physical properties and conditions for sampling site selection as well as the assessment of safe landing operations. TIR is based on a two-dimensional uncooled micro-bolometer array inherited from the Longwave Infrared Camera LIR on Akatsuki (Fukuhara et al., 2011). TIR takes images of thermal infrared emission in 8 to 12 μm with a field of view of 16×12∘16×12∘ and a spatial resolution of 0.05∘0.05∘ per pixel. TIR covers the temperature range from 150 to 460 K, including the well calibrated range from 230 to 420 K. Temperature accuracy is within 2 K or better for summed images, and the relative accuracy or noise equivalent temperature difference (NETD) at each of pixels is 0.4 K or lower for the well-calibrated temperature range. TIR takes a couple of images with shutter open and closed, the corresponding dark frame, and provides a true thermal image by dark frame subtraction. Data processing involves summation of multiple images, image processing including the StarPixel compression (Hihara et al., 2014), and transfer to the data recorder in the spacecraft digital electronics (DE). We report the scientific and mission objectives of TIR, the requirements and constraints for the instrument specifications, the designed instrumentation and the pre-flight and in-flight performances of TIR, as well as its observation plan during the Hayabusa2 mission.
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| 6. |
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| 7. |
- Puttnam, Benjamin J., et al.
(författare)
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0.61 Pb/s S, C, and L-Band Transmission in a 125 mu m Diameter 4-Core Fiber Using a Single Wideband Comb Source
- 2021
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 39:4, s. 1027-1032
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Tidskriftsartikel (refereegranskat)abstract
- We investigate high-throughput, multi-band transmission in a 4-core multi-core fiber (MCF) with the same 125 mu m cladding diameter of standard single-mode fiber (SMF). A single wideband comb source is used to transmit up to 561 wavelength channels with 25 GHz spacing over a 120 nm bandwidth in S, C, and L bands. We demonstrate a maximum decoded throughput of 610 Tb/s in PDM-256QAM and PDM-64QAM signals over a 54 km fiber, transmitting more than 155 Tb/s in a single core and measuring a per-core average throughput exceeding record transmission demonstrations in SMF. In addition, we use noise loading measurements to characterize the achievable signal quality across the wideband transmitter. These results show that a single comb source can enable high-spectral efficiency modulation over wide bandwidths and further that low-core count homogeneous MCF technology can offer the same transmission performance as single-mode fibers without sacrificing mechanical reliability, and still offering the benefits of shared resources and greater efficiency that drives SDM technologies.
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| 8. |
- Puttnam, Benjamin J., et al.
(författare)
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Characteristics of homogeneous multi-core fibers for SDM transmission
- 2019
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Ingår i: APL Photonics. - : AIP Publishing. - 2378-0967. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- We describe optical data transmission systems using homogeneous, single-mode, multi-core fibers (MCFs). We first briefly discuss space-division multiplexing (SDM) fibers, observing that no individual SDM fiber offers overwhelming advantages over bundles of single-mode fiber (SMF) across all transmission regimes. We note that for early adoption of SDM fibers, uncoupled or weakly coupled fibers which are compatible with existing SDM infrastructure have a practical advantage. Yet, to be more attractive than parallel SMF, it is also necessary to demonstrate benefits beyond improved spatial spectral efficiency. It is hoped that the lower spread of propagation delays (skew) between spatial channels in some fibers can be exploited for improved performance and greater efficiency from hardware sharing and joint processing. However, whether these benefits can be practically harnessed and outweigh impairments or effort to mitigate cross talk between spatial channels is not yet clear. Hence, focusing on homogeneous MCFs, we first describe measurements and simulations on the impact of inter-core cross talk in such fibers before reporting experimental investigation into the spatial channel skew variation with a series of the experimental results including a comparison with SMF in varying environmental conditions. Finally, we present some system and transmission experiments using parallel recirculating loops that enable demonstration of both multi-dimensional modulation and joint digital processing techniques across three MCF cores. Both techniques lead to increased transmission reach but highlight the need for further experimental analysis to properly characterize the potential benefits of correlated propagation delays in such fibers.
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| 9. |
- Rademacher, Georg, et al.
(författare)
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159 Tbit/s C+L Band Transmission over 1045 km 3-Mode Graded-Index Few-Mode Fiber
- 2018
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Ingår i: 2018 Optical Fiber Communications Conference and Exposition, OFC 2018 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- We transmit 3 x348 x 24.5 Gbaud PDM-16-QAM modulated C+L band channels with a total data-rate of over 159 Tbit/s over 1045 km graded-index three-mode fiber, resulting in a record throughput-distance product of more than 166 Pbit/sxkm.
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| 10. |
- Yabuta, Hikaru, et al.
(författare)
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Macromolecular organic matter in samples of the asteroid (162173) Ryugu
- 2023
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Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 379:6634
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Tidskriftsartikel (refereegranskat)abstract
- Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugus parent body.
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