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. (2010) Chromatic dispersion compensation in coherent transmission system using digital filters. Optics Express, 18 (15 Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way.Publisher's statement: © 2010 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited. http://dx.doi.org/10.1364/OE.18.016243 A note on versions: The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL' above for details on accessing the published version and note that access may require a subscription. Abstract:We present a comparative analysis of three popular digital filters for chromatic dispersion compensation: a time-domain least mean square adaptive filter, a time-domain fiber dispersion finite impulse response filter, and a frequency-domain blind look-up filter. The filters are applied to equalize the chromatic dispersion in a 112-Gbit/s non-return-to-zero polarization division multiplexed quadrature phase shift keying transmission system. The characteristics of these filters are compared by evaluating their applicability for different fiber lengths, their usability for dispersion perturbations, and their computational complexity. In addition, the phase noise tolerance of these filters is also analyzed.

. (2013) Carrier phase estimation methods in coherent transmission systems influenced by equalization enhanced phase noise. Optics Communications, 293. pp. 54-60. Permanent WRAP URL: http://wrap.warwick.ac.uk/93880 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL' above for details on accessing the published version and note that access may require a subscription. ABSTRACTWe present a comparative study on three carrier phase estimation algorithms, including a one-tap normalized least mean square (NLMS) method, a block-average method, and a Viterbi-Viterbi method in the n-level phase shift keying coherent transmission systems considering the equalization enhanced phase noise (EEPN). In these carrier phase estimation methods, the theoretical bit-error-rate floors based on traditional leading-order Taylor expansion are compared to the practical simulation results, and the tolerable total effective linewidths (involving the transmitter, the local oscillator lasers and the EEPN) for a fixed bit-error-rate floor are evaluated with different block size, when the fiber nonlinearities are neglected. The complexity of the three carrier phase estimation methods is also discussed. We find that the carrier phase estimation methods in practical systems should be analyzed based on the simulation results rather than the traditional theoretical predictions, when large EEPN is involved. The one-tap NLMS method can always show an acceptable behavior, while the step size is complicated to optimize. The block-average method is efficient to implement, but it behaves unsatisfactorily when using a large block size. The Viterbi-Viterbi method can show a small improvement compared to the block-average method, while it requires more computational complexity.

The electrocatalytic carbon dioxide reduction reaction (CO 2 RR) holds great potential in promoting carbon neutral through effectively converting CO 2 molecules to useful chemicals and fuels. The high-efficiency electrochemical conversion of CO 2 to single-carbon products has been well realized, while more efforts are needed for the generation of high-value multicarbon products. Metal−organic frameworks (MOFs), featuring porous structures, high chemical tunability, and ultralarge surface area, have attracted increasing attention in the electrochemical CO 2 RR. Herein, we review the recent progress of electrocatalytic CO 2 RR on MOF-based materials toward multicarbon products. First, the structure of MOFs is briefly introduced. Then, the electrocatalytic CO 2 RR performance and the corresponding catalytic mechanism of pristine MOFs (classified according to the kind of organic ligands/linkers) and MOF-derived materials (including metal nanomaterials, single-atom catalysts and nanocomposites) toward the multicarbon product generation are systematically discussed. Finally, critical challenges and potential opportunities are highlighted to inspire the rational design and targeted synthesis of advanced MOF-based materials for high-performance electrocatalytic CO 2 reduction toward multicarbon products.

Abstract:In this paper we present a comparative study in order to specify the influence of equalization enhanced phase noise (EEPN) for pre-and post-compensation of chromatic dispersion in high capacity and high constellation systems. This is -to our knowledge -the first detailed study in this area for pre-compensation systems. Our main results show that the local oscillator phase noise determines the EEPN influence in postcompensation implementations whereas the transmitter laser determines the EEPN in pre-compensation implementations. As a result of significance for the implementation of practical longer-range systems it is to be emphasized that the use of chromatic dispersion equalization in the optical domain -e.g. by the use of dispersion compensation fibers -eliminates the EEPN entirely. Thus, this seems a good option for such systems operating at high constellations in the future.

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Long-haul high speed optical transmission systems are significantly distorted by the interplay between the electronic chromatic dispersion (CD) equalization and the local oscillator (LO) laser phase noise, which leads to an effect of equalization enhanced phase noise (EEPN). The EEPN degrades the performance of optical communication systems severely with the increment of fiber dispersion, LO laser linewidth, symbol rate, and modulation format. In this paper, we present an analytical model for evaluating the performance of bit-error-rate (BER) versus signal-to-noise ratio (SNR) in the n-level

Background Potassium is a nutrient element necessary for tobacco growth. Tobacco leaves with high potassium content are elastic and tough, rich in oil. And the same time, potassium can also improve the scent and aromatic value of flue-cured tobacco by regulating the synthesis of aromatic hydrocarbons in leaves.. It is an important quality indicator for flue-cured tobacco. However, the potassium concentration in tobacco leaves in most areas of China is generally lower than the global standard for high quality tobacco. Two tobacco genotypes were grafted to each other under different potassium levels to test whether potassium content and plant growth can be improved by grafting in tobacco. Results The growth of tobacco in all treatments was inhibited under potassium starvation, and grafting significantly alleviated this potassium stress in ‘Yunyan 87’. The trends in whole plant K + uptake and K + transfer efficiency to the leaves corresponded to the growth results of the different grafts. The nutrient depletion test results showed that the roots of ‘Wufeng No.2’ had higher K + absorption potential, K + affinity, and K + inward flow rate. K + enrichment circles appeared at the endoderm of the root section in the energy dispersive X-ray figure, indicating that the formation of Casparian strips may be partly responsible for the lower rate of lateral movement of K + in the roots of ‘Yunyan 87’. Gene expression analysis suggested that energy redistribution at the whole plant level might constitute one strategy for coping with potassium starvation. The feedback regulation effects between scion ‘Wufeng No.2’ and rootstock ‘Yunyan 87’ indicated that the transmission of certain signaling substances had occurred during grafting. Conclusions ‘Wufeng No.2’ tobacco rootstock grafting can increase the K + uptake and transport efficiency of ‘Yunyan 87’ and enhance plant growth under potassium stress. The physiological mechanism of the improved performance of grafted tobacco is related to higher K + uptake and utilization ability, improved xylem K + loading capacity, and up-regulated expression of genes related to energy supply systems.