5 research outputs found
Underwater Optical Wireless Communication Systems: A Concise Review
Underwater optical wireless communications (UOWC) have gained a considerable interest during the last years as an alternative means for broadband inexpensive submarine communications. UOWC present numerous similarities compared to free space optical (FSO) communications or laser satellite links mainly due to the fact that they employ optical wavelengths to transfer secure information between dedicated point‐to‐point links. By using suitable wavelengths, high data rates can be attained. Some recent works showed that broadband links can be achieved over moderate ranges. Transmissions of several Mbps have been realized in laboratory experiments by employing a simulated aquatic medium with scattering characteristics similar to oceanic waters. It was also demonstrated that UOWC networks are feasible to operate at high data rates for medium distances up to a hundred meters. However, it is not currently available as an industrial product and mainly test‐bed measurements in water test tanks have been reported so far. Therefore, extensive research is expected in the near future, which is necessary in order to further reveal the “hidden” abilities of optical spectrum to transfer broadband signals at higher distances. The present work summarizes the recent advances in channel modeling and system analysis and design in the area of UOWC
Time Jitter, Turbulence and Chromatic Dispersion in Underwater Optical Wireless Links
The performance of an underwater optical wireless communication link is
investigated by taking into account-for the first time and to the best
of our knowledge-the simultaneous influence of the chromatic dispersion,
the time jitter and the turbulence effects, by assuming chirped
longitudinal Gaussian pulse propagation as information carriers. The
estimation procedure is presented and a novel probability density
function is extracted in order to describe the irradiance fluctuations
at the receiver side. Furthermore, the availability of the link is
investigated by means of its probability of fade and various numerical
results are presented using typical parameters for the underwater
optical wireless communication systems
Circuit Implementation of a Modified Chaotic System with Hyperbolic Sine Nonlinearities Using Bi-Color LED
In this paper, a chaotic three dimansional dynamical system is proposed, that is a modification of the system in Volos et al. (2017). The new system has two hyperbolic sine nonlinear terms, as opposed to the original system that only included one, in order to optimize system’s chaotic behavior, which is confirmed by the calculation of the maximal Lyapunov exponents and Kaplan-Yorke dimension. The system is experimentally realized, using Bi-color LEDs to emulate the hyperbolic sine functions. An extended dynamical analysis is then performed, by computing numerically the system’s bifurcation and continuation diagrams, Lyapunov exponents and phase portraits, and comparing the numerical simulations with the circuit simulations. A series of interesting phenomena are unmasked, like period doubling route to chaos, coexisting attractors and antimonotonicity, which are all verified from the circuit realization of the system. Hence, the circuit setup accurately emulates the chaotic dynamics of the proposed system
Circuit Implementation of a Modified Chaotic System with Hyperbolic Sine Nonlinearities Using Bi-Color LED
In this paper, a chaotic three dimansional dynamical system is proposed,
that is a modification of the system in Volos et al. (2017). The new
system has two hyperbolic sine nonlinear terms, as opposed to the
original system that only included one, in order to optimize system's
chaotic behavior, which is confirmed by the calculation of the maximal
Lyapunov exponents and Kaplan-Yorke dimension. The system is
experimentally realized, using Bi-color LEDs to emulate the hyperbolic
sine functions. An extended dynamical analysis is then performed, by
computing numerically the system's bifurcation and continuation
diagrams, Lyapunov exponents and phase portraits, and comparing the
numerical simulations with the circuit simulations. A series of
interesting phenomena are unmasked, like period doubling route to chaos,
coexisting attractors and antimonotonicity, which are all verified from
the circuit realization of the system. Hence, the circuit setup
accurately emulates the chaotic dynamics of the proposed system
Study on Optical Positioning Using Experimental Visible Light Communication System
Visible light positioning systems (VLP) have attracted significant commercial and research interest because of the many advantages they possess over other applications such as radio frequency (RF) positioning systems. In this work, an experimental configuration of an indoor VLP system based on the well-known Lambertian light emission, is investigated. The corresponding results are also presented, and show that the system retains high enough accuracy to be operational, even in cases of low transmitted power and high background noise