检索结果-南通市图书馆

Simultaneous 45.2 Gbit/s 4-PAM data and 8 GHz reference frequency clock signal transmission over DWDM VCSEL channels for optical interconnects

在线全文

学校读者我要写书评

暂无评论

Optoelectronics Letters 2019年第1期15卷 48-51页

作者： G.M.Isoe A.W.R.Leitch T.B.Gibbon centre for Broadband communication Nelson Mandela University

In this paper, we propose and experimentally demonstrate a vertical cavity surface emitting laser(VCSEL)-based simultaneous 45.2 Gbit/s(2×22.6 Gbit/s) 4-PAM data and 8 GHz(2×4 GHz) phase modulated reference frequency(RF) clock signal transmission dense wavelength division multiplexing(DWDM) system for optical interconnects. Two low-cost power-efficient 10 G VCSEL channels with central wavelengths at 1 550.71 nm and 1 551.11 nm are separately modulated with 22.6 Gbit/s 4-PAM data, therefore doubling the channel bit rate. Carrier spectral efficiency per channel is further maximized by exploiting the phase attribute in transmission of a 4 Hz RF clock signal. To further maximize the network capacity, the two VCSEL channels are densely multiplexed at 0.4 nm spacing. We therefore experimentally achieve the network data rate of 45.2 Gbit/s with 8 GHz phase modulated RF clock signal. The results show that receiver sensitivities of-11.02 dBm and-9.98 dBm are experimentally achieved for VCSEL channels of 1 550.71 nm and 1 551.11 nm respectively without the phase modulated RF clock signal. However, the introduction of a phase modulated clock signal contributes to a maximum interference penalty of 0.57 dBm and 0.41 dBm for the considered channels respectively. Simultaneous distribution of transmission data and reference clock signal over shared network structure maximizes the carrier spectral efficiency and network capacity with low cost.

关键词： VCSEL Simultaneous reference

VCSEL wavelength reuse for intrinsically bidirectional data traffics in next generation GPONs

在线全文

学校读者我要写书评

暂无评论

Optoelectronics Letters 2019年第5期15卷 360-362页

作者： G.M.Isoe S.Wassin T.B.Gibbon centre for Broadband communication Nelson Mandela University

An all-optical wavelength reuse technique employing cost effective power efficient vertical surface emitting laser(VCSEL) is proposed to address uplink data streaming from end-users by exploiting the same wavelength assigned to them. A saturated optical erbium-doped optical fiber amplifier(EDFA) is adopted to erase a directly modulated 10 Gbit/s data from an incoming downstream wavelength. We show that with EDFA saturation, the extinction ration of the incoming wavelength is reduced to less than 1 d Bm, therefore allowing for wavelength re-modulation. A receiver sensitivity of -19.65 d Bm and -17.86 d Bm is attained for downstream and upstream data signals respectively. A total of 24.7 km single mode fibre transmission is attained experimentally. This technique opens new perspectives towards development of efficient spectrum utilization for application in wavelength flexible optical networks with non-static flex-spectrum grids.

关键词： VCSEL erbium-doped optical fiber amplifier(EDFA) intrinsically bidirectional

Real-time 850 nm multimode VCSEL to 1 550 nm single mode VCSEL data routing for optical interconnects

在线全文

学校读者我要写书评

暂无评论

Optoelectronics Letters 2019年第4期15卷 297-301页

作者： G.M.Isoe A.W.R.Leitch T.B.Gibbon centre for Broadband communication Nelson Mandela University

Short-reach optical interconnects among massive serves in data centers have attracted extensive research recently. Increasing capacity, cost and power efficiency as well as wavelength switching between data center network nodes are still key challenges for current optical interconnects. In this work, we experimentally demonstrate the real-time intermode optical wavelength switching technique, for high-speed wavelength flexible data center interconnects. A10 Gbit/s 1 550 nm single mode vertical cavity surface emitting laser(VCSEL) is optically injected and used to control a 10 Gbit/s multimode VCSEL carrier at 850 nm. Results show that a clearly open eye diagram is achieved at back-to-back analysis, implying a successful wavelength switch and error-free operation at 10 Gbit/s. A fully optical wavelength conversion of a multimode VCSEL operation at 850 nm using a single mode VCSEL subject to external optical injection at 1 550 nm is reported. This work opens new perspectives towards the development of a cost effective high-speed real-time inter-band wavelength switching technique between servers and network devices operating at different transmission windows at network nodes, for current and future optical interconnects.

关键词： VCSEL optical interconnects data centers

Time and reference frequency transfer over 850 nm VCSEL for digital telecommunication network synchronization

在线全文

学校读者我要写书评

暂无评论

Optoelectronics Letters 2019年第3期15卷 209-212页

作者： G.M.Isoe S.Wassin A.W.R.Leitch T.B.Gibbon centre for Broadband communication Nelson Mandela University

Accurate time transfer and synchronization between different network nodes is a key functional requirement in digital communication. Developments in optical fiber-based frequency dissemination techniques have improved optical frequency stability over time to much lower levels. In this work, we experimentally present the reference frequency transfer employing 850 nm vertical cavity surface emitting laser(VCSEL) over 100.3 m OM3 multimode fiber for synchronization of clocks on networked devices such as servers and racks/pod at different data center network nodes. A low-cost power-efficient multimode VCSEL with central wavelength at 844.26 nm is directly modulated with a 2 GHz reference frequency(RF) clock signal, and transferred over 100.3 m of OM3 multimode fiber. The single side band(SSB) phase noise of-104.62 dBc/Hz and-100.70 dBc/Hz is experimentally measured at back-to-back(B2 B) and 100.3 m OM3 multimode fiber transmission respectively at a 1 kHz frequency offset. The jitter stability of 0.14 ps and 0.15 ps is experimentally achieved at B2 B and 100.3 m fiber transmission, respectively. This work provides an alternative viable approach for the development of time keeping devices in high-speed short-reach optical communication systems.

关键词： VCSEL

Joint channel estimation and beam selection NOMA system for satellite-based Internet of Things

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2022年第10期65卷 270-284页

作者： Zeqiong CHEN Jian JIAO Shaohua WU Qinyu ZHANG communication Engineering Research centre Harbin Institute of Technology (Shenzhen) Peng Cheng Laboratory

Multibeam low earth orbit(LEO) millimeter wave(mm Wave) band high throughput satellite(HTS) is regarded as a key component in the upcoming satellite-based Internet of Things(S-Io T). The multibeam LEO HTS with non-orthogonal multiple access(NOMA) can support global coverage and low latency broadband access over a wide geographical area in a cost-efficient manner. However, the performance is constrained by the channel state information and subsequent beam selection in multibeam LEO *** design a joint channel estimation and beam selection NOMA system for S-Io T in this paper, including the pseudo random ergodic(PRE)-throughput maximum(TM) scheme for massive multiple access, and the asynchronous CSI-assisted(AIA)-TM scheme for high throughput services. Moreover, we propose the PREfairness guaranteed(FG) and AIA-FG schemes for achieving better fairness with slightly loss of *** results show that the PRE-TM and AIA-TM schemes can adaptively reduce the required channel measurements, while approaching the optimal system throughput performance of the exhaust searching(ES)scheme with a much lower computational complexity.

关键词： satellite-based Internet of Things non-orthogonal multiple access channel estimation system throughput fairness

同方期刊数据库

Children＇s Expression of Voluntary Motion Events in English and Chinese

在线全文

学校读者我要写书评

暂无评论

外国语 2011年第4期34卷 2-20页

作者：纪瑛琳 Henri■tte Hendriks Maya Hickmann centre for Language Discourse and CommunicationDepartment of Education and Professional StudiesKing's College Research centre for English and Applied Linguistics University of Cambridge CNRS Laboratoire Structures Formelles du Langage and University of Paris 8

尽管人类对空间的认知可能具有一定的普遍性,但人类对同一空间事件的表达却因为语言的差异而千差万别。本研究旨在探讨英汉儿童如何表达基于动画的自主性运动事件。我们发现英语及汉语在空间表达上的类型学差异制约着儿童在小句层面上... 详细信息

尽管人类对空间的认知可能具有一定的普遍性,但人类对同一空间事件的表达却因为语言的差异而千差万别。本研究旨在探讨英汉儿童如何表达基于动画的自主性运动事件。我们发现英语及汉语在空间表达上的类型学差异制约着儿童在小句层面上惯于表达的信息成分的类型及数量。汉语儿童在空间表达上的语句比同龄英语儿童的语句具有更高的信息密度,并且差异显著。这主要是因为汉语中的动词复合形式极大地促进了多重语义成分在同一小句中的同时体现。另外,英语儿童在3至5岁之间经历了空间表达方式上的重要发展,而相比之下汉语儿童的空间表达从3岁起就展现出了一些与成人的空间表达极为相似的特征。本研究揭示了语言独特性因素在语言习得中所起的重要作用。

关键词：普遍认知能力语言独特性因素动词复合形式信息密度

Transmission of precise phase coherent optical signals using a VCSEL stabilization system

在线全文

学校读者我要写书评

暂无评论

Optoelectronics Letters 2019年第3期15卷 200-203页

作者： Shukree Wassin George Isoe Andrew Leitch Tim Gibbon centre for Broadband communication Physics DepartmentNelson Mandela University

To improve the time and frequency reference standards used for radio astronomy and high precision atomic physics applications, we describe a novel stable frequency transmission technique. The approach uses a vertical-cavity surface-emitting laser(VCSEL) based phase correction actuator. Using a frequency mixing process for feedback control, the phase noise induced along the 26 km G.655 optical fibre link was actively reduced. This was achieved by using a 1 310 nm dither controlled VCSEL phase error correction actuator together with the inherent chromatic dispersion properties of the fibre. The technique corrects phase noise and optical signal drift along the fibre at the transmission end. Fractional frequency instabilities across the G.655 fibre link of 4.44×10-12 at 1 s and 4.86×10-14 at 104 s are successfully reported.

关键词： VCSEL Transmission of precise phase coherent optical signals using a VCSEL stabilization system

Future Directions in Formulaic Language Research

在线全文

学校读者我要写书评

暂无评论

外国语 2009年第6期32卷 2-17页

作者： Alison Wray centre for Language and communication Research Cardiff University

Research tends to go in cycles of innovation,consolidation and confirmation,then *** language research seems currently to be moving into a reflective phase,offering considerable potential for new ideas feeding the next round of *** into formulaic language goes back 150 years at least,with several strands developing somewhat independently,including patterns in native language (including first language acquisition),language disorders and second language *** own work was an attempt to identify a single explanation that accounted for them *** technologies now provide additional ways to explore and evaluate the evidence,most notably through corpus linguistics,and eye and brain activity *** key claims,all with potential implications for L2 research and teaching,indicate the scope for future research:*** we talk of an 'idiomatic' nativelike way of speaking,in fact there is considerable variation in what is idiomatic:what should be taught? *** acquisition of idiomaticity is driven by the need to belong and survive:can this be replicated in the classroom? *** formulaic language seems to reduce the speaker' s processing,the hearer' s processing may be the more important consideration:does 'accommodation' affect the learner's experience adversely? *** linguistics forces a careful evaluation of the true role of frequency in idiomaticity:are materials writers beguiled by corpus data? *** cannot consider formulaic language patterns independently of knowing the purpose of the text in which they occur,including its genre:are L2 teaching materials broad enough?There are key opportunities for researchers in China to exploit aspects of the Chinese writing system and approach to education,to answer questions that cannot be easily answered in the *** include the role of memorisation in language learning,the role of literacy in our perception of linguistic units,and the universality of patterns in acqu

关键词：语言学语义学语用学外语学习

VCSEL-based Raman technology for extended reach time and reference frequency transfer systems

在线全文

学校读者我要写书评

暂无评论

Optoelectronics Letters 2019年第2期15卷 139-143页

作者： G.M.Isoe E.K.Rotich T.B.Gibbon centre for Broadband communication Nelson Mandela University

This paper experimentally demonstrates a low-cost energy efficient alternative technique for long reach transfer of accurate reference frequency(RF) clock signals for extended reach RF distribution *** is achieved by adopting distributed forward Raman amplification and vertical cavity surface emitting laser(VCSEL) technology.A class 10 G VCSEL is directly modulated with a 2 GHz RF clock *** exploiting a forward Raman pump with the flat gain of 8.6 dB, a 100.8-km-long standard single mode fiber(SMF) RF clock distribution is experimentally achieved.A maximum phase noise of-117.66 dBc/Hz at offset frequency of 100 kHz and an RF clock jitter(RMS) of 5.36 ps is experimentally measured for 100.8-km-long fiber transmission without forward Raman ***, with the adoption of forward Raman amplification, the measured phase noise and RMS improves to-86.59 dBc/Hz and 1.7 ps, *** Raman pumping offers distributed high flat gain over a wide spectra range(over 35.5 nm), while VCSELs offer cost effective broadband signal distribution, therefore keeping the network optics investment low.

关键词： technology reference amplification