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RISS 인기검색어
- 검색키워드
- 저자 : Changyuan Yu (검색결과 3 건)
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Zhou, Jingjing,Yu, Changyuan,Mohan, Gurusamy,Kim, Hoon IEEE 2016 Journal of lightwave technology Vol.34 No.16
<P>We explore the possibility of transmitting 25-Gb/s ON-OFF keying (OOK) signals generated by using a 1.5-mu m 10G-class vertical-cavity surface-emitting laser (VCSEL) over standard single-mode fiber (SSMF) for optical access applications. A transistor-outline-can packaged VCSEL having a 3-dB modulation bandwidth of 7 GHz is utilized to transmit the 25-Gb/s signals. We experimentally investigate the transmission performances of OOK signals obtained from two different transmitter schemes: with and without a delay interferometer (DI) at the output of the directly modulated VCSEL. In order to maximize the transmission distance without using bulky and lossy dispersion compensation modules, we optimize the extinction ratio of the signals and apply the electrical equalization at the receiver. Also optimized is the free-spectral range (FSR) of the DI when it is utilized. The experimental results show that we can successfully transmit the 25-Gb/s OOK signals over 33- and 45-km long SSMF with and without the DI, respectively. The use of DI not only alleviates the band limitation of the VCSEL but also significantly improves the receiver sensitivity of the 25-Gb/s OOK signal up to 30 km. Moreover, a larger power budget is achieved for transmission distances shorter than 25 km when a DI having an FSR of 25 GHz is utilized at the output of the VCSEL.</P>
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Jingjing Zhou,Changyuan Yu,Hoon Kim IEEE 2015 Journal of lightwave technology Vol.33 No.15
<P>We evaluate the possibility of realizing optical access networks using 1.5-mu m vertical-cavity surface-emitting lasers (VCSELs) in the on-off keying (OOK) and four-level pulse amplitude modulation (4-PAM) formats. In order to maximize the power budget of the networks, we optimize the extinction ratio of the 10.7- and 21.4-Gb/s signals and exploit the electrical equalization at the receiver. The experimental comparison made at 10.7 Gb/s shows that the OOK format vastly outperforms the 4-PAM format in terms of tolerance to chromatic dispersion. For example, we achieve the 80-km transmission of the OOK signal over standard single-mode fiber (SSMF), but the maximum reach is halved when the 4-PAM signal is employed. Nevertheless, the 4-PAM format is still an effective way to double the data rate of the VCSEL links in optical access networks. We successfully transmit the 21.4-Gb/s 4-PAM signal generated by using the 1.5-mu m VCSEL over 18-km long SSMF.</P>
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Identification of Dominant Microbial Community and Diversity in Continuously Cropped Pepper Fields
Hui Wang,Li Liu,Shuyi Yu,Tianshu Guan,Baihong Li,Qi Wang,Changyuan Liu 한국원예학회 2021 원예과학기술지 Vol.39 No.4
Pepper blight is the most significant soil-borne disease affecting the continuous cropping of peppers. To identify the effect of Phytophthora capsici infection on microbial flora, we isolated and counted the microorganisms collected from the rhizosphere soil of P. capsici-affected farms that continuously cropped pepper for 3, 6, and 9 years in Liaoning Province, China. The colony and cell morphology, physiological and biochemical characteristics, and 16S rDNA sequence of bacteria and actinomycetes were documented. In addition, colony and microscopic morphology of fungi and the rDNA-ITS sequence were analysed for classification. We observed that healthy and diseased peppers had the largest number of bacteria in the rhizosphere followed by actinomycetes and fungi. After infection, the number of bacteria and actinomycetes decreased with a corresponding increase in the number of fungi, leading to a reduction in the ratio of bacteria/fungi to actinomycetes/fungi. We identified 15 dominant bacterial strains, of which Bacillus represented the most abundant genus consisting of 7 strains followed by Flavobacterium and Staphylococcus. Furthermore, 15 of the 17 actinomycetes strains belonged to the genus Streptomyces. Among the six fungal strains, we found P. infestans, Fusarium, and Penicillium consisting of two strains each. This study elucidated the impact of pathogenic P. capsici on the composition of soil microbes over time and characterized several cultivatable dominant bacterial groups, which can provide a basis for practical intervention strategies to improve soil conditions for continuous cropping.
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