Search results for "Bandwidth"
showing 10 items of 250 documents
SmartSpectra: Applying multispectral imaging to industrial environments
2005
SmartSpectra is a smart multispectral system for industrial, environmental, and commercial applications where the use of spectral information beyond the visible range is needed. The SmartSpectra system provides six spectral bands in the range 400-1000nm. The bands are configurable in terms of central wavelength and bandwidth by using electronic tunable filters. SmartSpectra consists of a multispectral sensor and the software that controls the system and simplifies the acquisition process. A first prototype called Autonomous Tunable Filter System is already available. This paper describes the SmartSpectra system, demonstrates its performance in the estimation of chlorophyll in plant leaves, …
On the Benefits of Random Linear Coding for Unicast Applications in Disruption Tolerant Networks
2006
In this paper, we investigate the benefits of using a form of network coding known as Random Linear Coding (RLC) for unicast communications in a mobile Disruption Tolerant Network (DTN) under epidemic routing. Under RLC, DTN nodes store and then forward random linear combinations of packets as they encounter other DTN nodes. We first consider the case where there is a single block of packets propagating in the network and then consider the case where blocks of K packets arrive according to a Poisson arrival process. Our performance metric of interest is the delay until the last packet in a block is delivered. We show that for the single block case, when bandwidth is constrained, applying RL…
Channel Modeling and System Concepts for Future Terahertz Communications: Getting Ready for Advances Beyond 5G
2020
Future terahertz (THz) communications will utilize the frequency spectrum around 300 GHz. This technology provides a promising solution for future high-data-rate communications due to the high available bandwidth. However, the unfavorable channel characteristics are a major barrier for the realization of THz communications. To address the challenges caused by the unfavorable propagation conditions, the world?s first THz communication standard includes a channel-modeling document (CMD).
Bottle microresonator with actively stabilized evanescent coupling
2011
The evanescent coupling of light between a whispering-gallery-mode bottle microresonator and a sub-wavelength-diameter coupling fiber is actively stabilized by means of a Pound-Drever-Hall technique. We demonstrate the stabilization of a critically coupled resonator with a control bandwidth of 0.1 Hz, yielding a residual transmission of (9 \pm 3) \times 10^-3 for more than an hour. Simultaneously, the frequency of the resonator mode is actively stabilized.
3.5-μm bandwidth mid-infrared supercontinuum generation in a 2-cm long suspended-core chalcogenide fiber
2014
A supercontinuum source extending from 0.6 to 4.1 µm has been successfully generated in a 2-cm long As2S3 chalcogenide suspended-core fiber by means of a nJ-level 200-fs pumping at 2.5 µm.
Inverse dispersion design in silicon waveguides
2014
We present a numerical tool to find the cross-section geometry of silicon-oninsulator waveguides that leads to a target dispersion profile. In < 10 iterations, we achieve geometries providing ultraflattened dispersion over 350 nm bandwidth.
FLUMO: FLexible Underwater MOdem
2019
The last years have seen a growing interest in underwater acoustic communications because of its applications in marine research, oceanography, marine commercial operations, the offshore oil industry and defense. High-speed communication in the underwater acoustic channel has been challenging because of limited bandwidth, extended multipath, refractive properties of the medium, severe fading, rapid time variation and large Doppler shifts. In this paper, we show an implementation of a flexible Software-Defined Acoustic (SDA) underwater modem, where modulation parameters are completely tunable to optimize performance. In particular, we develop the system architecture following two key ideas. …
Enabling Searches on Wavelengths in a Hyperspectral Indices Database
2018
Abstract. Spectral indices derived from hyperspectral reflectance measurements are powerful tools to estimate physical parameters in a non-destructive and precise way for several fields of applications, among others vegetation health analysis, coastal and deep water constituents, geology, and atmosphere composition. In the last years, several micro-hyperspectral sensors have appeared, with both full-frame and push-broom acquisition technologies, while in the near future several hyperspectral spaceborne missions are planned to be launched. This is fostering the use of hyperspectral data in basic and applied research causing a large number of spectral indices to be defined and used in various…
Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy
2013
The noise of the frequency-shift signal Δf in noncontact atomic force microscopy (NC-AFM) consists of cantilever thermal noise, tip–surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density dz at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density dΔf at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip–surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacemen…
A Channel-Aware Adaptive Modem for Underwater Acoustic Communications
2021
Acoustic underwater channels are very challenging, because of limited bandwidth, long propagation delays, extended multipath, severe attenuation, rapid time variation and large Doppler shifts. A plethora of underwater communication techniques have been developed for dealing with such a complexity, mostly tailoring specific applications scenarios which can not be considered as one-size-fits-all solutions. Indeed, the design of environment-specific solutions is especially critical for modulations with high spectral efficiency, which are very sensitive to channel characteristics. In this paper, we design and implement a software-defined modem able to dynamically estimate the acoustic channel c…