8 research outputs found
Radio over fiber broadband access networks architectures based on wavelength division multiplexing techniques
The recent remarkable growth in bandwidth of both wired optical and wireless access
networks supports a burst of new high bandwidth Internet applications such as: peer-topeer
file sharing, cloud storage, on-line gaming, video streaming, etc. Within this
scenario, the convergence of fixed and wireless access networks offers significant
opportunities for network operators to satisfy user demands, and simultaneously reduce
the cost of implementing and running separated wireless and wired networks.
The integration of wired and wireless network can be accomplished within several
scenarios and at several levels. In this thesis we will focus on converged radio over fiber
architectures, particularly on two application scenarios: converged optical 60 GHz
wireless networks and wireless overlay backhauling over bidirectional colorless
wavelength division multiplexing passive optical networks (WDM-PONs).
In the first application scenario, optical 60 GHz signal generation using external
modulation of an optical carrier by means of lithium niobate (LiNbO3) Mach- Zehnder
modulators (MZM) is considered. The performance of different optical modulation
techniques, robust against fiber dispersion is assessed and dispersion mitigation strategies
are identified. The study is extended to 60 GHz carriers digitally modulated with data and
to systems employing subcarrier multiplexed (SCM) mm-wave channels.
In the second application scenario, the performance of WDM-PONs employing
reflective semiconductor optical amplifiers (RSOAs), transmitting an overlay orthogonal
frequency-division multiplexing (OFDM) wireless signal is assessed analytically and
experimentally, with the relevant system impairments being identified. It is demonstrated
that the intermodulation due to the beating of the baseband signal and wireless signal at
the receiver can seriously impair the wireless channel. Performance degradation of the
wireless channel caused by the RSOA gain modulation owing to the downstream
baseband data is also assessed, and system design guidelines are provided.Universidade do Algarve, Faculdade de Ciências e Tecnologi
Lanthanide-based complexes as efficient physiological temperature sensors
A new molecular thermometric sensor based on the terbium(III) complex [C2mim][Tb(fod)4] (C2mim – 1-methyl-3-ethylimidazolium, fod− - tetrakis-6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate), doped with 0.015% of its europium(III) analogue (1, [C2mim][Tb(fod)4]0.99985:[C2mim][Eu(fod)4]0.00015), was prepared and its thermochromic behaviour evaluated from ambient temperature up to 75 °C, including in the physiological range (35–45 °C). It was found that the intensity ratio of the 5D4→7F5 (TbIII) and 5D0→7F2 (EuIII) transitions is correlated with temperature having three different linear regimes. Visual colorimetry allowed the evaluation of the temperature in different ranges from green at ambient temperature, to yellow and finally red at higher temperatures. The TbIII complex emission intensity is extremely sensitive to small temperature variations, particularly between 25 and 35 °C, were it reaches only 40% of the initial intensity.
Confinement of the dopped TbIII tetrakis-complex in the organic polymeric matrix poly(methylmethacrylate) (PMMA) induced higher thermal stability in 1, together with a strong temperature dependence of the most intense emissive transition of the TbIII complexes. The photoluminescence quantum yield of polymer-lanthanide hybrid materials increased significantly compared with that of 1. Under 366 nm irradiation, the hybrid material presents a green colour at 25 °C that evolves to yellow at 30 °C and to a white tone at 35 °C.publishe
RoFnet – Reconfigurable Radio over Fiber Network Architecture Overview, Journal of Telecommunications and Information Technology, 2009, nr 1
This paper introduces the basic operational concepts of the RoFnet – reconfigurable radio over fiber network, which is a project supported by the Portuguese Foundation forScience and Technology. This project proposes an innovative radio over fiber optical access network architecture, which combines a low cost base station (BS) design, incorporating reflective semiconductor optical amplifiers, with fiber dispersion mitigation provided by optical single sideband modulation techniques. Optical wavelength division multiplexing (WDM) techniques are used to simplify the access network architecture allowing for different BSs to be fed by a common fiber. Different wavelength channels can be allocated to different BSs depending on user requirements. Additionally, in order to improve radio coverage within a cell, it is considered a sectorized antenna interface. The combination of subcarrier multiplexing with WDM, further simplifies the network architecture, by using a specific wavelength channel to feed an individual BS and different subcarriers to drive the individual antenna sectors within the BS
Transmission Performance of mm-Waves on Radio over Fiber Systems: Dispersion and Intermodulation Issues
International audienceNext generation wireless networks must provide high broadband access, which can be achieved by combining the fiber optics and wireless technologies. In this paper we analyze a mm-wave radio over fiber (RoF) optical access network architecture, combining radio subcarrier multiplexing techniques to improve system efficiency with fiber dispersion mitigation provided by optical single sideband modulation techniques. Our results show the system degradation introduced by the fiber link, namely fiber dispersion and intermodulation effects
Stochastic induced dynamics in neuromorphic optoelectronic oscillators
We investigate the dynamics of optoelectronic oscillator (OEO) systems based on resonant tunneling diode photodetector (RTD-PD) and laser diode hybrid integrated circuits. We demonstrate that RTD-based OEOs can be noise-activated in either monostable or bistable operating conditions, providing a rich variety of signal outputs—spiking, square pulses, bursting—and behaviours—stochastic and coherence resonances—that are similar to that of biological systems such as neurons. The potential for fully monolithic integration of our OEO confers them a great potential in novel neuromorphic optoelectronic circuits for signal processing tasks including re-timing and re-shaping of pulsed signals exploiting either the monostable or the bistable operating conditions
Stochastic induced dynamics in neuromorphic optoelectronic oscillators
© Springer Science+Business Media New York 2013. We investigate the dynamics of optoelectronic oscillator (OEO) systems based on resonant tunneling diode photodetector (RTD-PD) and laser diode hybrid integrated circuits. We demonstrate that RTD-based OEOs can be noise-activated in either monostable or bistable operating conditions, providing a rich variety of signal outputs—spiking, square pulses, bursting—and behaviours—stochastic and coherence resonances—that are similar to that of biological systems such as neurons. The potential for fully monolithic integration of our OEO confers them a great potential in novel neuromorphic optoelectronic circuits for signal processing tasks including re-timing and re-shaping of pulsed signals exploiting either the monostable or the bistable operating conditions.J.J. acknowledges financial support from the Ramon y Cajal fellowship. B.R. thanks FCT Portugal for a Postdoctoral Fellowship (Grant FRH/BPD/84466/2012). J.J. and S.B. acknowledge financial support from project RANGER (TEC2012-38864-C03-01) and from the Direcció General de Recerca del Govern de les Illes Balears and the FEDER fundsPeer Reviewe
Menthol and Menthone Associated with Acetylsalicylic Acid and Their Relation to the Hepatic Fibrosis in Schistosoma mansoni Infected Mice
Schistosomiasis is an important parasitic disease caused by Schistosoma mansoni, an intravascular trematode. Schistosomiasis treatment is limited to just one drug, Praziquantel (PZQ). Thus, studies on new antischistosomal compounds are of fundamental importance to disease control. Here we report on the effects of Mentha piperita L. compounds – menthol and menthone – in association with acetylsalicylic acid (ASA) in the regulation of hepatic fibrosis caused by schistosomiasis granulomas. Six different groups of Swiss rats were infected with 80 cercariae. Two groups received only menthol and menthol treatment at different concentrations (30 and 50 mg/kg); two groups received treatment with the same concentration of menthol and menthol, but associated the ASA. All groups received treatment for 14 consecutive days from the 35 days after the parasitic infection. In addition, three other groups were used: uninfected and untreated group, infected and untreated group and infected group treated with the commercial drug (single dose). Parasitological, cytological and histological analyses were performed. Results showed a significant reduction on the number of eosinophils found in the peritoneal cavity lavage (LPC) in all treated groups and on the number of eosinophils found in the blood of PZQ treated group, in the blood of the group treated with 30 mg/kg of Mentaliv® and in the blood of group treated with 50 mg/kg Mentaliv® + ASA when compared to the infected group. All treated groups presented a reduction in the parasite load, represented by the number of S. mansoni eggs, in the experimental group treated with 30 mg/kg of menthol and menthone a 62.80% reduction was observed and in the experimental group treated with 50 mg/kg of menthol and menthone + ASA a reduction of 64.21% was observed. In the liver histological analysis we observed that all Mentaliv® treated groups expressed a unique cytological profile, with diffused cells through the granuloma. In the experimental group treated with 50 mg/kg of Mentaliv® + ASA it was possible to observe the formation of type III collagen fibers, a typical wound healing characteristic. Our data strongly suggest that both the hepatic fibrosis and the inflammatory process were regulated through the schistosomiasis granulomatous process after treatment with menthol and menthone associated with ASA