Bandwidth studies on multimode polymer waveguides for ≥ 25 Gb/s optical interconnects

Multimode polymer waveguides constitute a promising technology for use in board-level optical interconnects. However, the continuous improvements in high-speed performance of VCSELs raise important questions about their ability to support such high data rates due to their inherent highly-multimoded nature. Thorough experimental studies on the bandwidth of a 1.4 m long multimode spiral waveguide are presented in this paper, indicating a bandwidth-length product of at least 35 GHz×m even in the case of an overfilled launch. No significant transmission impairments are observed for spatial input offsets, while error-free (BER<10⁻¹²) data transmission over the 1.4 m long spiral waveguide is demonstrated at 25 Gb/s.This is the final version of the article. It first appeared from IEEE Photonics Technology Letters via http://dx.doi.org/10.1109/LPT.2014.2342881. © © 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

High-bandwidth and low-loss multimode polymer waveguides and waveguide components for high-speed board-level optical interconnects

Multimode polymer waveguides are being increasingly considered for use in short-reach board-level optical interconnects as they exhibit favourable optical properties and allow direct integration onto standard PCBs with conventional methods of the electronics industry. Siloxane-based multimode waveguides have been demonstrated with excellent optical transmission performance, while a wide range of passive waveguide components that offer routing flexibility and enable the implementation of complex on-board interconnection architectures has been reported. In recent work, we have demonstrated that these polymer waveguides can exhibit very high bandwidth-length products in excess of 30 GHz×m despite their highly-multimoded nature, while it has been shown that even larger values of > 60 GHz×m can be achieved by adjusting their refractive index profile. Furthermore, the combination of refractive index engineering and launch conditioning schemes can ensure high bandwidth (> 100 GHz×m) and high coupling efficiency (< 1 dB) with standard multimode fibre inputs with relatively large alignment tolerances (~17×15 μm^2 ). In the work presented here, we investigate the effects of refractive index engineering on the performance of passive waveguide components (crossings, bends) and provide suitable design rules for their on-board use. It is shown that, depending on the interconnection layout and link requirements, appropriate choice of refractive index profile can provide enhanced component performance, ensuring low loss interconnection and adequate link bandwidth. The results highlight the strong potential of this versatile optical technology for the formation of high-performance board-level optical interconnects with high routing flexibility.The authors would like to acknowledge Dow Corning for the provision of the polymer samples and the UK EPSRC for supporting this work . Additional data related to this publication is available at the University of Cambridge data repository ( https://www.repository.cam.ac.uk/handle/1810/253542).This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by SPIE

Prevalence of Mycobacterium tuberculosis in Taiwan: A Model for Strain Evolution Linked to Population Migration

The global evolution and spread of Mycobacterium tuberculosis (MTB), one of the most successful bacterial pathogens, remain a mystery. Advances in molecular technology in the past decade now make it possible to understand MTB strain evolution and transmission in the context of human population migration. Taiwan is a relatively isolated island, serving as a mixing vessel over the past four centuries as colonization by different waves of ethnic groups occurred. By using mycobacterial tandem repeat sequences as genetic markers, the prevalence of MTB strains in Taiwan revealed an interesting association with historical migrations of different ethnic populations, thus providing a good model to explore the global evolution and spread of MTB

Dispersion studies on multimode polymer spiral waveguides for board-level optical interconnects

Dispersion studies are conducted on 1m long multimode polymer spiral waveguides with different refractive index profiles. Bandwidth-length products >40GHzxm are obtained from such waveguides under a 50/125 um MMF, indicating the potential of this technology.The authors would like to acknowledge Dow Corning for providing the waveguide samples and EPSRC for supporting the work.This is the accepted manuscript. The final version is available at http://dx.doi.org/10.1109/OIC.2015.711567

The relationship between web enjoyment and student perceptions and learning using a web-based tutorial

Web enjoyment has been regarded as a component of system experience. However, there has been little targeted research considering the role of web enjoyment alone in student learning using web-based systems. To address this gap, this study aims to examine the influence of web enjoyment on learning performance and perceptions by controlling system experience as a variable in the study. 74 students participated in the study, using a web-based tutorial covering subject matter in the area of 'Computation and algorithms'. Their learning performance was assessed with a pre-test and a post-test and their learning perceptions were evaluated with a questionnaire. The results indicated that there are positive relationships between the levels of web enjoyment and perceived usefulness and non-linear navigation for users with similar, significant levels of system experience. The implications of these findings in relation to web-based learning are explored and ways in which the needs of students who report different levels of web enjoyment might be met are discussed

A UHF RFID Reader Antenna with Tunable Axial Ratio and Fixed Beamwidth

A novel ultra-high-frequency (UHF) RFID reader antenna is proposed. The antenna has a unique property as being able to change its axial ratio (AR) without affecting its gain, beamwidth or impedance matching performance, enabling the isolated study of the effect of different axial ratios in RFID tag reading.This work was supported by EPSRC EP /S-19405/1 Channel Optimised Distributed Passive Sensor Networks

Novel Digital Radio over Fiber (DRoF) System with Data Compression for Neutral-Host Fronthaul Applications

© 2013 IEEE. Digital radio-over-fibre transmission has been studied extensively as a way of providing seamless last-mile wireless connectivity by carrying digitised radio frequency (RF) services over broadband optical infrastructures. With the growing demand on wireless capacity and the number of wireless services, a key challenge is the enormous scale of the digital data generated after the digitisation process. In turn, this leads to optical links needing to have very large capacity and hence, high capital expenditure (CAPEX). In this paper, we firstly present and then experimentally demonstrate a multiservice DRoF system for a neutral-host fronthaul link where both forward and reverse links use data compression, multiband multiplexing and synchronisation algorithms. The effect of a novel digital automatic gain control (DAGC) is comprehensively analysed to show an improved RF dynamic range alongside bit rate reduction. In this case, the system allows all cellular services from the three Chinese mobile network operators (MNOs) to be converged onto a single fiber infrastructure. We successfully demonstrate 14 wireless channels over a 10Gbps 20km optical link for indoor and outdoor wireless coverage, showing a minimum error value magnitude (EVM) of 60dB RF dynamic range. It is believed that the technology provides an ideal solution for last-mile wireless coverage in 5G and beyond

Beam Scanning UHF RFID Reader Antenna with High Gain and Wide Axial Ratio Beamwidth

A novel ultra-high-frequency (UHF) RFID reader antenna is proposed, designed and measured. The proposed antenna is capable of 2-dimensional (2D) beam-scanning from 0º to 360º in the azimuth plane, and 0º to 40º in the zenith plane. The minima of the antenna's axial ratio (AR) follows its gain maxima during beam-scanning, resulting in an equivalent 3 dB AR beamwidth of over 136º for every phi cut. Moreover, the antenna's AR can be easily modified without affecting other parameters. It is shown experimentally that the antenna's 2D beam-scanning ability and the improved AR performance lead to better tag-reading results, improving the percentage of missing tags by up to 21.6% compared to a standard antenna which has a degraded AR and only supports 1D beam-scanning. In addition, the antenna needs no matching network and has a -10 dB return loss bandwidth from 860 MHz to 880 MHz.This work was supported by EPSRC EP /S-19405/1 Channel Optimised Distributed Passive Sensor Network

Costunolide causes mitotic arrest and enhances radiosensitivity in human hepatocellular carcinoma cells

<p>Abstract</p> <p>Purpose</p> <p>This work aimed to investigate the effect of costunolide, a sesquiterpene lactone isolated from <it>Michelia compressa</it>, on cell cycle distribution and radiosensitivity of human hepatocellular carcinoma (HCC) cells.</p> <p>Methods</p> <p>The assessment used in this study included: cell viability assay, cell cycle analysis by DNA histogram, expression of phosphorylated histone H3 (Ser 10) by flow cytometer, mitotic index by Liu's stain and morphological observation, mitotic spindle alignment by immunofluorescence of alpha-tubulin, expression of cell cycle-related proteins by Western blotting, and radiation survival by clonogenic assay.</p> <p>Results</p> <p>Our results show that costunolide reduced the viability of HA22T/VGH cells. It caused a rapid G2/M arrest at 4 hours shown by DNA histogram. The increase in phosphorylated histone H3 (Ser 10)-positive cells and mitotic index indicates costunolide-treated cells are arrested at mitosis, not G2, phase. Immunofluorescence of alpha-tubulin for spindle formation further demonstrated these cells are halted at metaphase. Costunolide up-regulated the expression of phosphorylated Chk2 (Thr 68), phosphorylated Cdc25c (Ser 216), phosphorylated Cdk1 (Tyr 15) and cyclin B1 in HA22T/VGH cells. At optimal condition causing mitotic arrest, costunolide sensitized HA22T/VGH HCC cells to ionizing radiation with sensitizer enhancement ratio up to 1.9.</p> <p>Conclusions</p> <p>Costunolide could reduce the viability and arrest cell cycling at mitosis in hepatoma cells. Logical exploration of this mitosis-arresting activity for cancer therapeutics shows costunolide enhanced the killing effect of radiotherapy against human HCC cells.</p

Striatal dopamine D₂/₃ receptors in medication-naïve schizophrenia: an [¹²³I] IBZM SPECT study

BACKGROUND: The hyper-function of the striatal dopamine system has been suggested to underlie key pathophysiological mechanisms in schizophrenia. Moreover, patients have been observed to present a significant elevation of dopamine receptor availability compared to healthy controls. Although it is difficult to measure dopamine levels directly in humans, neurochemical imaging techniques such as single-photon emission computed tomography (SPECT) provide indirect indices of in vivo dopamine synthesis and release, and putative synaptic levels. METHODS: We focused on the role of dopamine postsynaptic regulation using [123I] iodobenzamide (IBZM) SPECT. We compared D2/3 receptor availability between 53 healthy controls and 21 medication-naive patients with recent-onset schizophrenia. RESULT: The mean specific striatal binding showed no significant difference between patients and controls (estimated difference = 0.001; 95% CI -0.11 to 0.11; F = 0.00, df = 1, 69; p = 0.99). There was a highly significant effect of age whereby IBZM binding declined with advancing age [estimated change per decade of age = -0.01(binding ratio); 95% CI -0.01 to -0.004; F = 11.5, df = 1, 69; p = 0.001]. No significant correlations were found between the mean specific striatal binding and psychopathological or cognitive rating scores. CONCLUSIONS: Medication-naïve patients with recent-onset schizophrenia have similar D2/3 receptor availability to healthy controls. We suggest that, rather than focusing exclusively on postsynaptic receptors, future treatments should target the presynaptic control of dopamine synthesis and release