1,721,065 research outputs found
A 3D indoor positioning system based on common visible LEDs
Get PDFWe propose a realistic 3D positioning system for indoor navigation that exploits visible Light EmittingDiodes (LEDs), placed on the ceiling. A unique frequency tone is assigned to each lamp and modulatesits intensity in periodic time slots. The Time Difference of Arrival (TDOA) is measured without theneed of a synchronization system between the sources and the receiver, then it is used to accuratelyestimate the receiver position. We first describe the theoretical approach, then propose the modeland characterize the possible sources of noise. Finally, we demonstrate the proof-of-concept of theproposed system by simulation of lightwave propagation. Namely, we assess its performance by usingMontecarlo simulations in a common room and estimate the impact of the different implementationparameters on the accuracy of the proposed solution. We find that, in realistic conditions, thetechnique allows for centimeter precision. Pushing the device requirements, the precision can befurther increased to a sub-centimeter accuracy
New Prospects of Optical Wireless Communication Systems Exploiting VCSEL-Based Transmitters
Get PDFIn the last decades, Vertical Cavity Surface Emitting Lasers (VCSELs) emerged as a dominant technology for shortreach high-data rate networks thanks to several advantageous features. These include low power consumption, high modulation speeds, low costs, and compact size. More recently, these inherent characteristics of the VCSELs have also made them exceptionally suited for a variety of Optical Wireless Communication (OWC) applications, particularly for short-distance links, up to a few meters. This paper reviews a range of new and promising applications for VCSELs within emerging OWC domains: Data Centers (DCs), space, and harsh environment. We present and discuss different VCSEL-based OWC systems that were designed, implemented, and tested in these emerging scenarios. For the DCs scenario, we present a novel approach to establish OWC links able to reach data rates up to 40 Gbit/s with a single VCSEL. In the space environment, innovative OWC systems can support data communication among electronic elements placed in line-of-sight outside the spacecraft or inside a small satellite. VCSELs can be also exploited for data transmission in the very harsh environment of high-energy physics experiments. Here, a 10 Gbit/s OWC system was designed for the Board-to-Board (B2B) link in High Energy Physics (HEP) experiments. Since space and HEP applications exhibit extreme conditions, the OWC systems and, particularly, the VCSELs were tested to assess their behavior under strong mechanical, thermal, and radiation stress
Optical vs. electrical duobinary coding for 25 Gb/s PONs based on DSP-free coherent envelope detection
No full textWe investigate and experimentally compare 25 Gb/s serial-line rate optical and electrical duobinary signals combined with DSP-free, coherent envelope-detection for serial-line rate upgrade in future PONs. -37.3dBm sensitivity is achieved without applying any equalization
Modelization and characterization of a CMOS camera as an optical real-time oscilloscope
Get PDFComplementary Metal-Oxide Semiconductor (CMOS) camera sensors are embedded in many consumer electronics products: Thanks to the Rolling Shutter (RS) readout mode, they can detect a time-varying light intensity, which is the key to realize Optical Camera Communication (OCC). To this aim, we introduce here a model describing the camera as a Real-Time Oscilloscope (RTO) detecting optical signals; by means of this approach, we can now characterize the Complementary Metal-Oxide Semiconductor (CMOS) camera by means of parameters that correspond to common oscilloscope specifications, such as the frequency response, the noise, the Signal to Noise Ratio (SNR), the total harmonic distortion (THD), etc.; all of these are introduced and measured in terms of the camera parameters. This approach provides for the first time a set of quantitative tools that should be used to maximize the OCC transmission performance by allowing the optimal selection of the camera settings
Contemplata aliis tradere: ciaramella e liuto, un organico mariano? Savoldo contemplativo
No full textE’ individuata l’antinomia della pala dipinta dal Savoldo nel 1524-1525 per l’altare maggiore della chiesa dei Domeicani in Pesaro: ciaramella e liuto sono un insieme musicale impossibile. Altra anomalia: nessuno dei due strumenti suona. Si ipotizza un possibile significato in relazione ai Domenicani in Pesaro (divenuta nel 1523 di fatto capitale del ducato d’Urbino), al probabile ruolo di Leonora Gonzaga (il cui musico prediletto Marcantonio Cavazzoni è tra i testimoni del contratto), alla esigenza cattolica di riforma della Chiesa e alla protesta di Lutero. Alcune sequenze proprie dei Domenicani aiutano la lettura dell’immagine; affidandosi a Maria, stella del mare dove si lavora alacremente a riformare la nave della Chiesa, il desiderio di un’unità capace di silenzio permette la conciliazione degli opposti
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
All-optical signal reshaping via Four-Wave Mixing in optical fibers
No full textA new scheme for all-optical signal reshaping is proposed and demonstrated. The strongly depleted mixing between a CW pump and a noisy nonreturn-to-zero (NRZ) signal in a common fiber can provide wavelength-converted signals exhibiting excellent intensity-noise cancellation. Numerical simulations confirm almost complete suppression of intensity fluctuations, simultaneously occurring at several different wavelength
System feasibility of using stimulated Brillouin scattering in self coherent detection schemes
Get PDFWe demonstrate the first self-coherent detection of 10 Gbit/s BPSK signals based on narrow-band amplification of the optical carrier by means of Stimulated Brillouin effect in a common fiber. We found that this technique is very effective only if it is combined with proper line coding and high-pass electrical filtering at the receiver. In this case we obtain OSNR-performance close to the ideal coherent receiver. (C) 2010 Optical Society of Americ
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