Search results for "Free Space Optic"
showing 10 items of 20 documents
Contribution à l'étude des liaisons optiques atmosphériques : propagation, disponibilité et fiabilité.
2005
In this work we study the fog attenuation in the visible and infrared spectral band related to Free Space Optics (FSO). Based on the Mie scattering theory, fog extinction coefficients for different particle size distributions as a function of wavelength were derived. A simple analytical model allowing the prediction of atmospheric transmission for the 0.69 - 1.55 µm spectral band was developed. This model is valid for advection and convection fog and for visibility range between 50 to 1000 m. This model, implemented into software developed at FT R&D, allows the prediction of the Quality of Service of FSO links. Finally, we performed an experimental study to compare the fog effect on two FSO…
Error mitigation using RaptorQ codes in an experimental indoor free space optical link under the influence of turbulence
2015
In free space optical (FSO) communications, several factors can strongly affect the link quality. Among them, one of the most important impairments that can degrade the FSO link quality and its reliability even under the clear sky conditions consists of optical turbulence. In this work, the authors investigate the generation of both weak and moderate turbulence regimes in an indoor environment to assess the FSO link quality. In particular, they show that, due to the presence of the turbulence, the link experiences both erasure errors and packet losses during transmission, and also compare the experimental statistical distribution of samples with the predicted Gamma Gamma model. Furthermore,…
Recovery Capabilities of Rateless Codes on Simulated Turbulent Terrestrial Free Space Optics Channel Model
2013
Free Space Optics (FSO) links are affected by several impairments: optical turbulence, scattering, absorption, and pointing. In particular, atmospheric optical turbulence generates optical power fluctuations at the receiver that can degrade communications with fading events, especially in high data rate links. Innovative solutions require an improvement of FSO link performances, together with testing models and appropriate channel codes. In this paper, we describe a high-resolution time-correlated channel model able to predict random temporal fluctuations of optical signal irradiance caused by optical turbulence. Concerning the same channel, we also report simulation results on the error mi…
Packet loss recovery in an indoor Free Space Optics link using rateless codes
2014
Free Space Optics (FSO) systems present some important advantages if compared to Radio Frequency links, but they can be affected by several impairments that degrade the link quality and availability. In particular, due to temporary interruptions of the line-of-sight condition between the transmitter and the receiver, packet loss can occur during data transmission. In this work, we present an indoor Free Space Optics link, in which we have systematically generated interruptions of the beam. We demonstrate how the application of the most recent rateless codes, i.e., RaptorQ codes, can strongly improve the link quality by reducing packet loss. In particular, results show that the Packet Error …
Analyses of Dual Polarization WDM and SCM Radio over Fiber and Radio over FSO for C-RAN Architecture
2016
En este trabajo se simulan y verifican experimentalmente los esquemas de transmisión para una Arquitectura de Red de Acceso Radio Centralizada (C-RAN) basados en la combinación de dos tecnologías: Radio sobre Fibra (RoF) y Radio sobre FSO (RoFSO). Las configuraciones propuestas se optimizan para la evolución a largo plazo (LTE) con un ancho de banda de 20 MHz utilizando una modulación de amplitud en cuadratura de 64-QAM en términos de magnitud de vector de error (EVM). En primer lugar, se comparan las mediciones de la multiplexación por división de polarización mediante la combinación de RoF y RoFSO (PDM-RoF/FSO) con los modelos de simulación. Esto se amplía con la combinación de PDM-Multip…
Rateless codes mitigation technique in a turbulent indoor Free Space Optics link
2014
Free Space Optics (FSO) links are affected by several impairments and, among them, optical turbulence is the most important factor that can degrade the link quality. Due to the presence of this phenomenon, the signal irradiance detected by the receiver fluctuates, thus causing erasure errors and fading events. In this work, we present an indoor Free Space Optics link, in which several turbulence conditions are generated by using two heating elements. We show that the generated turbulence causes erasure errors and packet losses during the data transmission, and we also compare the statistical distribution of the samples with the theoretical models. Moreover, we demonstrate how the applicatio…
Model Analysis of Hydrometeor Scattering Effects on Free Space Near-Infrared Links
2012
A promising technology for peer-to-peer connections and urban area networks is represented by wireless communications through free space using optical carrier (Free Space Optics, FSO). This technology ensures high data rates, with relatively low error rates, low power consumption and inherent security. Nevertheless FSO links are quite sensitive to atmospheric condition. Fog droplets, but also raindrops and snowflakes, may introduce severe path attenuation which drastically reduces the channel availability. A parametric model to simulate droplets scattering effects over the FSO link in terms of extinction coefficient, albedo factor and asymmetry coefficient as function of the particle water …
Moderate-to-Strong Turbulence Generation in a Laboratory Indoor Free Space Optics Link and Error Mitigation via RaptorQ Codes
2016
Free Space Optics (FSO) is rapidly gaining interest as a line-of sight communication technology that offers capabilities similar - in terms of bandwidth and transfer rates - to optical fibre, also possessing several advantages compared with traditional radio frequency links. However, FSO link quality can be strongly affected by unfavourable weather conditions and also by the phenomenon of optical turbulence, even in clear sky. In this work, we have implemented an indoor FSO link and generated moderate-to-strong turbulence conditions along the optical path by using heaters and a mechanical ventilation system. In this way, we have been able to investigate the effects of the generated turbulen…
Rateless Codes Performance Tests On Terrestrial FSO Time-Correlated Channel Model
2012
Free Space Optics (FSO) links are affected by several impairments: optical turbulence, scattering, absorption, and pointing. In particular, atmospheric optical turbulence generates optical power fluctuations at the receiver that can degrade communications with fading events, especially, in high data rate links. A way to mitigate FSO link outages can be to add a coding to communications. Nevertheless, in order to study innovative solutions (software or hardware) and to improve the FSO link performance it needs accurate testing models. In this paper we describe an accurate time-correlated channel model able to predict random temporal fluctuations of optical signal irradiance caused by optical…
Rateless codes implementation, optimization and application to Free Space Optics links affected by optical turbulence
In this work, I have implemented, optimized and tested the most advanced rateless codes available up to now, i.e., RaptorQ codes. In detail, a multiplatform data transmission software has been appositely developed in order to verify the effectiveness of the above-mentioned codes to decrease packet loss and hence to improve the link quality, under different network and channel conditions. Several simulative and experimental investigations have been carried out to evaluate the performance of the encoding and decoding schemes and the relative recovery capabilities under different test scenarios. In particular, I have applied the software embedding RaptorQ codes to Free Space Optics communicati…