J R Souza - Academia.edu (original) (raw)
Papers by J R Souza
Soliton control with fixed- and sliding-frequency filters: a feasibility study
Proceedings of the 2001 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference. (Cat. No.01TH8568)
In this paper the spectral filtering technique is deployed for soliton control. The objective of ... more In this paper the spectral filtering technique is deployed for soliton control. The objective of the work is to evaluate the performance of amplified soliton systems for application in long haul and/or high-speed transmissions. A numerical model based on the split-step Fourier solution of the nonlinear Schrodinger equation is used for extensive simulations in realistic conditions. Eye diagrams are used
Numerical Evidence for Hysteresis in Nonlinear Slab-Guided TE and TM Waves
20th European Microwave Conference, 1990, 1990
By means of finite difference methods, together with variational techniques, solutions are obtain... more By means of finite difference methods, together with variational techniques, solutions are obtained for both TE and TM waves guided by dielectric slabs surrounded by arbitrarily nonlinear material, illustrating the onset of bistability and hysteresis. The method relies on an iterative scheme to arrive at self-consistent and stable solutions. The dependence of the signal intensity threshold for the occurrence of
IEE Proceedings H Microwaves, Optics and Antennas, 1982
A coaxial to microstrip transition is characterised in terms of S-parameters, thus enabling a sim... more A coaxial to microstrip transition is characterised in terms of S-parameters, thus enabling a simple correction to be applied to measurements made on devices in microstrip. The transition, the model of which includes a fixed length of the microstrip line, is represented by S-parameters which are simple linear functions of frequency over the band 2-4 GHz. A simple computer program may be used to de-embed a device in the microstrip, or to calculate the expected values of the S-parameters at the inputs to the coaxial transitions when a known device is inserted into the microstrip line.
Ultra Short Pulse Propagation on Nonuniform Planar Transmission Lines
Applications of Photonic Technology, 1995
This paper presents a rigorous investigation of the propagation characteristics of short electric... more This paper presents a rigorous investigation of the propagation characteristics of short electric pulses on nonuniform planar transmission lines. For this purpose, frequency and time domain analyses are carried out by means of the Spectral Domain Approach and Fast Fourier Transform, respectively. This combined analysis shows if and how a pulse is distorted as it propagates down the nonuniform transmission line, and in consequence how the pulse distortion can be controlled through adjustments on the geometry of the transmission line. The results of this investigation find applications in high speed optoelectronics.
IEEE Photonics Technology Letters, 1990
In this letter we present numerical solutions of nonlinear optical waveguides illustrating the on... more In this letter we present numerical solutions of nonlinear optical waveguides illustrating the onset of bistability and the hysteresis nature for the symmetrical step index, asymmetrical step index, and asymmetrical diffused slab waveguides. Two different numerical techniques have been independently used-a finite element method (FEM) and a wriational method (VM). Both methods produce numericallystable solutions and agreement between them is good for both increasing and decreasing total power from below or above the threshold power. We have also compared our results with analytical solutions for these structures. The onset and the end of the physically unstable solutions coincides with the two power thresholds for the increasing and decreasing powers. A waveguide is taken to be defined by a refractive index prolile n(x, y , IEI), and we seek modal solutions of the form:
Anais do XX Simpósio Brasileiro de Telecomunicações, 2003
Resumo-Sistemas Ópticos no Espaço estão sendo desenvolvidos em todo o mundo como uma alternativa ... more Resumo-Sistemas Ópticos no Espaço estão sendo desenvolvidos em todo o mundo como uma alternativa econômica à tecnologia de fibra óptica nas mais diversas aplicações. A principal desvantagem destes sistemas é sua vulnerabilidade a efeitos atmosféricos. Este trabalho apresenta um consistente estudo da viabilidade de implantação destes sistemas nas diversas regiões brasileiras. Foi desenvolvido um modelo numérico, baseado no conceito de balanço de potência, que analisa as diferentes contribuições para a perda total em um enlace óptico. Os resultados, inéditos na literatura, são apresentados na forma de disponibilidade em função do alcance do enlace e indicam boa confiabilidade dos sistemas em algumas regiões do país. Palavras-Chave-Comunicações ópticas, sistemas ópticos no espaço livre.
IEEE Latin America Transactions, 2011
This work investigates how the allocation of channels-keeping the system bandwidth constant-affec... more This work investigates how the allocation of channels-keeping the system bandwidth constant-affects the FWM penalties imposed on DWDM systems. Different schemes are investigated, based on spacings ranging from 100 to 6.25 GHz. The results, not reported in the literature yet, indicate that some of them reduce the FWM.
Engevista, 2010
O presente trabalho investiga o efeito da alocação de canais nas penalidades impostas pelo mecani... more O presente trabalho investiga o efeito da alocação de canais nas penalidades impostas pelo mecanismo de mistura de quatro ondas (FWM - Four-Wave Mixing) em sistemas DWDM (Dense Wavelength Division Multiplexing) baseados em fibras monomodo de dispersão deslocada (G.653), mantendo constante a largura de banda do sistema. A potência de FWM, calculada sob a hipótese de bombeio sem depleção, é usadapara determinar a taxa de erro de bits (BER), tomada como medida do desempenho dos sistemas. São considerados seis esquemas de alocação de canais: espaçamento uniforme (EU), duplo espaçamento uniforme (EU-EU), espaçamento não uniforme (ENU), espaçamento não uniforme repetido (ENUR), espaçamento não uniforme refletido (ENU- 2) e espaçamento randômico (RAND), baseados nas grades de 100, 50, 25, 12,5 e 6,25 GHz. Os resultados, inéditos na literatura, investigam como, para uma dada BER, a potência total de sinal na entrada da fibra deve ser variada em função do posicionamento e número de canais, d...
IEEE Latin America Transactions, 2016
Unmanned systems are of great importance in accomplishing tasks where human lives are at risk. Th... more Unmanned systems are of great importance in accomplishing tasks where human lives are at risk. These systems are being deployed in tasks that are time-consuming, expensive or inconclusive if accomplished by human intervention. Design, development and testing of such vehicles using actual hardware could be quite costly and dangerous. Another issue is the limited outdoor usage permitted by Federal Aviation Administration regulations, which makes outdoor testing difficult. An optimal solution to this problem is to have a simulation environment where different operational scenarios, newly developed models, etc., can be studied. In this paper, we propose GNSSim, a Global Navigation Satellite System (GNSS) simulation framework. We demonstrate its effectiveness by integrating it with UAVSim. This allows users to experiment easily by adjusting different satellite as well as UAV parameters. Related tests and evidence of the correctness of the implementation are presented.
Numerical schemes for optical soliton propagation analysis: a test comparison
ABSTRACT
A Comparative Study of Techniques to Control Power Transients in Optical WDM Networks
ABSTRACT
Millimeter and Submillimeter Waves, 1994
The effects of planar transmission line dispersion, as well as dielectric and ground plane losses... more The effects of planar transmission line dispersion, as well as dielectric and ground plane losses, on the propagation of pico-second electric pulses are investigated. For this purpose, the Spectral Domain Approach (SDA) and Fast Fourier Transform (FFT) are used, to operate in the frequency and time domain, respectively. It is observed that the transmission line dispersion is the main cause for distortion of the pulses, while the material losses are mainly responsible for signal attenuation. It is also observed that the dispersive nature of the transmission line can be used with advantage, through careful choice of the line geometry and composition, to reshape asymmetrical pulses, and to compress wide electrical pulses. The results of this study find applications on quasi-optical circuits and short optical pulse generation.
Microwave and Optical Technology Letters, 1990
route to chaos through period doubling as the guided-wave power increases.
Frequency-dependent characteristics of thick microstrip lines in lossy multilayered dielectric media
International Journal of Infrared and Millimeter Waves, 1993
ABSTRACT
Engevista, 2010
O presente trabalho investiga o efeito da alocação de canais nas penalidades impostas pelo mecani... more O presente trabalho investiga o efeito da alocação de canais nas penalidades impostas pelo mecanismo de mistura de quatro ondas (FWM - Four-Wave Mixing) em sistemas DWDM (Dense Wavelength Division Multiplexing) baseados em fibras monomodo de dispersão deslocada (G.653), mantendo constante a largura de banda do sistema. A potência de FWM, calculada sob a hipótese de bombeio sem depleção, é usadapara determinar a taxa de erro de bits (BER), tomada como medida do desempenho dos sistemas. São considerados seis esquemas de alocação de canais: espaçamento uniforme (EU), duplo espaçamento uniforme (EU-EU), espaçamento não uniforme (ENU), espaçamento não uniforme repetido (ENUR), espaçamento não uniforme refletido (ENU- 2) e espaçamento randômico (RAND), baseados nas grades de 100, 50, 25, 12,5 e 6,25 GHz. Os resultados, inéditos na literatura, investigam como, para uma dada BER, a potência total de sinal na entrada da fibra deve ser variada em função do posicionamento e número de canais, d...
Assessment of higher order exponential operators for the simulation of high-capacity optical communication systems by the split-step fourier method
Journal of Microwaves and Optoelectronics, 2003
ABSTRACT
IEEE Latin America Transactions, 2016
Unmanned systems are of great importance in accomplishing tasks where human lives are at risk. Th... more Unmanned systems are of great importance in accomplishing tasks where human lives are at risk. These systems are being deployed in tasks that are time-consuming, expensive or inconclusive if accomplished by human intervention. Design, development and testing of such vehicles using actual hardware could be quite costly and dangerous. Another issue is the limited outdoor usage permitted by Federal Aviation Administration regulations, which makes outdoor testing difficult. An optimal solution to this problem is to have a simulation environment where different operational scenarios, newly developed models, etc., can be studied. In this paper, we propose GNSSim, a Global Navigation Satellite System (GNSS) simulation framework. We demonstrate its effectiveness by integrating it with UAVSim. This allows users to experiment easily by adjusting different satellite as well as UAV parameters. Related tests and evidence of the correctness of the implementation are presented.
Journal of Microwaves and Optoelectronics
IMPT reduced physical dose hot spots by 1.4% (median, PZ.23), and consistently covered the CTV wi... more IMPT reduced physical dose hot spots by 1.4% (median, PZ.23), and consistently covered the CTV with higher doses (PZ.19). Relative to IMRT, the brain V 10 was reduced in all IMPT plans by 56% (PZ.002), as well for max and mean doses for all OARs with statistical significance at 95% (e.g., chiasm median max dose was 11% lower, PZ.03). No significant max dose differences were seen at the brainstem surface (PZ.065); the core consistently received less dose with IMPT (PZ.03), emphasizing sharper achievable gradients in proton beams. Even using 4cm range shifters for superficial lesions, there were no significant skin dose differences between IMRT and IMPT (max dose and V 45 ); IMPT reduced brain V 70 by 9% (PZ.004). In consideration of dose-escalation, pediatric patients would benefit from potential reduction in OAR and integral dose achieved with IMPT. Because lack of GTV coverage correlates with reduced tumor control, protocol patient selection regarding OAR overlap has to be carefully considered.
IEEE Latin America Transactions, 2013
This paper presents a literature review of passive optical networks, and a realistic discussion o... more This paper presents a literature review of passive optical networks, and a realistic discussion of the current situation, including trends and market forecasts. The main characteristics of a PON network are highlighted, and the BPON, EPON, and GPON standards are compared. Experts believe the GPON standard will be the main technology by 2013. The study also shows that the deployment of PON networks is growing rapidly, particularly in Asia and the United States, where they account for 74% and 15% of all connections, respectively. In Latin America, the PON subscribers correspond to only 0.02% of the total. The first installations of the so-called GigaPON era (10 Gb/s operation rate together with WDM technology) have already begun.
Microwave and Optical Technology Letters, 2003
The four-wave mixing (FWM) process in single-mode optical fibers is investigated by considering t... more The four-wave mixing (FWM) process in single-mode optical fibers is investigated by considering that a zero-dispersion wavelength varies along the length of the fiber link, which is represented as a series of segments with different lengths, propagation constants, and zero-dispersion wavelengths. The results indicate that new optical frequencies are efficiently generated for particular combinations of the input-signal wavelengths, even when the phase-matching condition is not fully met.
Soliton control with fixed- and sliding-frequency filters: a feasibility study
Proceedings of the 2001 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference. (Cat. No.01TH8568)
In this paper the spectral filtering technique is deployed for soliton control. The objective of ... more In this paper the spectral filtering technique is deployed for soliton control. The objective of the work is to evaluate the performance of amplified soliton systems for application in long haul and/or high-speed transmissions. A numerical model based on the split-step Fourier solution of the nonlinear Schrodinger equation is used for extensive simulations in realistic conditions. Eye diagrams are used
Numerical Evidence for Hysteresis in Nonlinear Slab-Guided TE and TM Waves
20th European Microwave Conference, 1990, 1990
By means of finite difference methods, together with variational techniques, solutions are obtain... more By means of finite difference methods, together with variational techniques, solutions are obtained for both TE and TM waves guided by dielectric slabs surrounded by arbitrarily nonlinear material, illustrating the onset of bistability and hysteresis. The method relies on an iterative scheme to arrive at self-consistent and stable solutions. The dependence of the signal intensity threshold for the occurrence of
IEE Proceedings H Microwaves, Optics and Antennas, 1982
A coaxial to microstrip transition is characterised in terms of S-parameters, thus enabling a sim... more A coaxial to microstrip transition is characterised in terms of S-parameters, thus enabling a simple correction to be applied to measurements made on devices in microstrip. The transition, the model of which includes a fixed length of the microstrip line, is represented by S-parameters which are simple linear functions of frequency over the band 2-4 GHz. A simple computer program may be used to de-embed a device in the microstrip, or to calculate the expected values of the S-parameters at the inputs to the coaxial transitions when a known device is inserted into the microstrip line.
Ultra Short Pulse Propagation on Nonuniform Planar Transmission Lines
Applications of Photonic Technology, 1995
This paper presents a rigorous investigation of the propagation characteristics of short electric... more This paper presents a rigorous investigation of the propagation characteristics of short electric pulses on nonuniform planar transmission lines. For this purpose, frequency and time domain analyses are carried out by means of the Spectral Domain Approach and Fast Fourier Transform, respectively. This combined analysis shows if and how a pulse is distorted as it propagates down the nonuniform transmission line, and in consequence how the pulse distortion can be controlled through adjustments on the geometry of the transmission line. The results of this investigation find applications in high speed optoelectronics.
IEEE Photonics Technology Letters, 1990
In this letter we present numerical solutions of nonlinear optical waveguides illustrating the on... more In this letter we present numerical solutions of nonlinear optical waveguides illustrating the onset of bistability and the hysteresis nature for the symmetrical step index, asymmetrical step index, and asymmetrical diffused slab waveguides. Two different numerical techniques have been independently used-a finite element method (FEM) and a wriational method (VM). Both methods produce numericallystable solutions and agreement between them is good for both increasing and decreasing total power from below or above the threshold power. We have also compared our results with analytical solutions for these structures. The onset and the end of the physically unstable solutions coincides with the two power thresholds for the increasing and decreasing powers. A waveguide is taken to be defined by a refractive index prolile n(x, y , IEI), and we seek modal solutions of the form:
Anais do XX Simpósio Brasileiro de Telecomunicações, 2003
Resumo-Sistemas Ópticos no Espaço estão sendo desenvolvidos em todo o mundo como uma alternativa ... more Resumo-Sistemas Ópticos no Espaço estão sendo desenvolvidos em todo o mundo como uma alternativa econômica à tecnologia de fibra óptica nas mais diversas aplicações. A principal desvantagem destes sistemas é sua vulnerabilidade a efeitos atmosféricos. Este trabalho apresenta um consistente estudo da viabilidade de implantação destes sistemas nas diversas regiões brasileiras. Foi desenvolvido um modelo numérico, baseado no conceito de balanço de potência, que analisa as diferentes contribuições para a perda total em um enlace óptico. Os resultados, inéditos na literatura, são apresentados na forma de disponibilidade em função do alcance do enlace e indicam boa confiabilidade dos sistemas em algumas regiões do país. Palavras-Chave-Comunicações ópticas, sistemas ópticos no espaço livre.
IEEE Latin America Transactions, 2011
This work investigates how the allocation of channels-keeping the system bandwidth constant-affec... more This work investigates how the allocation of channels-keeping the system bandwidth constant-affects the FWM penalties imposed on DWDM systems. Different schemes are investigated, based on spacings ranging from 100 to 6.25 GHz. The results, not reported in the literature yet, indicate that some of them reduce the FWM.
Engevista, 2010
O presente trabalho investiga o efeito da alocação de canais nas penalidades impostas pelo mecani... more O presente trabalho investiga o efeito da alocação de canais nas penalidades impostas pelo mecanismo de mistura de quatro ondas (FWM - Four-Wave Mixing) em sistemas DWDM (Dense Wavelength Division Multiplexing) baseados em fibras monomodo de dispersão deslocada (G.653), mantendo constante a largura de banda do sistema. A potência de FWM, calculada sob a hipótese de bombeio sem depleção, é usadapara determinar a taxa de erro de bits (BER), tomada como medida do desempenho dos sistemas. São considerados seis esquemas de alocação de canais: espaçamento uniforme (EU), duplo espaçamento uniforme (EU-EU), espaçamento não uniforme (ENU), espaçamento não uniforme repetido (ENUR), espaçamento não uniforme refletido (ENU- 2) e espaçamento randômico (RAND), baseados nas grades de 100, 50, 25, 12,5 e 6,25 GHz. Os resultados, inéditos na literatura, investigam como, para uma dada BER, a potência total de sinal na entrada da fibra deve ser variada em função do posicionamento e número de canais, d...
IEEE Latin America Transactions, 2016
Unmanned systems are of great importance in accomplishing tasks where human lives are at risk. Th... more Unmanned systems are of great importance in accomplishing tasks where human lives are at risk. These systems are being deployed in tasks that are time-consuming, expensive or inconclusive if accomplished by human intervention. Design, development and testing of such vehicles using actual hardware could be quite costly and dangerous. Another issue is the limited outdoor usage permitted by Federal Aviation Administration regulations, which makes outdoor testing difficult. An optimal solution to this problem is to have a simulation environment where different operational scenarios, newly developed models, etc., can be studied. In this paper, we propose GNSSim, a Global Navigation Satellite System (GNSS) simulation framework. We demonstrate its effectiveness by integrating it with UAVSim. This allows users to experiment easily by adjusting different satellite as well as UAV parameters. Related tests and evidence of the correctness of the implementation are presented.
Numerical schemes for optical soliton propagation analysis: a test comparison
ABSTRACT
A Comparative Study of Techniques to Control Power Transients in Optical WDM Networks
ABSTRACT
Millimeter and Submillimeter Waves, 1994
The effects of planar transmission line dispersion, as well as dielectric and ground plane losses... more The effects of planar transmission line dispersion, as well as dielectric and ground plane losses, on the propagation of pico-second electric pulses are investigated. For this purpose, the Spectral Domain Approach (SDA) and Fast Fourier Transform (FFT) are used, to operate in the frequency and time domain, respectively. It is observed that the transmission line dispersion is the main cause for distortion of the pulses, while the material losses are mainly responsible for signal attenuation. It is also observed that the dispersive nature of the transmission line can be used with advantage, through careful choice of the line geometry and composition, to reshape asymmetrical pulses, and to compress wide electrical pulses. The results of this study find applications on quasi-optical circuits and short optical pulse generation.
Microwave and Optical Technology Letters, 1990
route to chaos through period doubling as the guided-wave power increases.
Frequency-dependent characteristics of thick microstrip lines in lossy multilayered dielectric media
International Journal of Infrared and Millimeter Waves, 1993
ABSTRACT
Engevista, 2010
O presente trabalho investiga o efeito da alocação de canais nas penalidades impostas pelo mecani... more O presente trabalho investiga o efeito da alocação de canais nas penalidades impostas pelo mecanismo de mistura de quatro ondas (FWM - Four-Wave Mixing) em sistemas DWDM (Dense Wavelength Division Multiplexing) baseados em fibras monomodo de dispersão deslocada (G.653), mantendo constante a largura de banda do sistema. A potência de FWM, calculada sob a hipótese de bombeio sem depleção, é usadapara determinar a taxa de erro de bits (BER), tomada como medida do desempenho dos sistemas. São considerados seis esquemas de alocação de canais: espaçamento uniforme (EU), duplo espaçamento uniforme (EU-EU), espaçamento não uniforme (ENU), espaçamento não uniforme repetido (ENUR), espaçamento não uniforme refletido (ENU- 2) e espaçamento randômico (RAND), baseados nas grades de 100, 50, 25, 12,5 e 6,25 GHz. Os resultados, inéditos na literatura, investigam como, para uma dada BER, a potência total de sinal na entrada da fibra deve ser variada em função do posicionamento e número de canais, d...
Assessment of higher order exponential operators for the simulation of high-capacity optical communication systems by the split-step fourier method
Journal of Microwaves and Optoelectronics, 2003
ABSTRACT
IEEE Latin America Transactions, 2016
Unmanned systems are of great importance in accomplishing tasks where human lives are at risk. Th... more Unmanned systems are of great importance in accomplishing tasks where human lives are at risk. These systems are being deployed in tasks that are time-consuming, expensive or inconclusive if accomplished by human intervention. Design, development and testing of such vehicles using actual hardware could be quite costly and dangerous. Another issue is the limited outdoor usage permitted by Federal Aviation Administration regulations, which makes outdoor testing difficult. An optimal solution to this problem is to have a simulation environment where different operational scenarios, newly developed models, etc., can be studied. In this paper, we propose GNSSim, a Global Navigation Satellite System (GNSS) simulation framework. We demonstrate its effectiveness by integrating it with UAVSim. This allows users to experiment easily by adjusting different satellite as well as UAV parameters. Related tests and evidence of the correctness of the implementation are presented.
Journal of Microwaves and Optoelectronics
IMPT reduced physical dose hot spots by 1.4% (median, PZ.23), and consistently covered the CTV wi... more IMPT reduced physical dose hot spots by 1.4% (median, PZ.23), and consistently covered the CTV with higher doses (PZ.19). Relative to IMRT, the brain V 10 was reduced in all IMPT plans by 56% (PZ.002), as well for max and mean doses for all OARs with statistical significance at 95% (e.g., chiasm median max dose was 11% lower, PZ.03). No significant max dose differences were seen at the brainstem surface (PZ.065); the core consistently received less dose with IMPT (PZ.03), emphasizing sharper achievable gradients in proton beams. Even using 4cm range shifters for superficial lesions, there were no significant skin dose differences between IMRT and IMPT (max dose and V 45 ); IMPT reduced brain V 70 by 9% (PZ.004). In consideration of dose-escalation, pediatric patients would benefit from potential reduction in OAR and integral dose achieved with IMPT. Because lack of GTV coverage correlates with reduced tumor control, protocol patient selection regarding OAR overlap has to be carefully considered.
IEEE Latin America Transactions, 2013
This paper presents a literature review of passive optical networks, and a realistic discussion o... more This paper presents a literature review of passive optical networks, and a realistic discussion of the current situation, including trends and market forecasts. The main characteristics of a PON network are highlighted, and the BPON, EPON, and GPON standards are compared. Experts believe the GPON standard will be the main technology by 2013. The study also shows that the deployment of PON networks is growing rapidly, particularly in Asia and the United States, where they account for 74% and 15% of all connections, respectively. In Latin America, the PON subscribers correspond to only 0.02% of the total. The first installations of the so-called GigaPON era (10 Gb/s operation rate together with WDM technology) have already begun.
Microwave and Optical Technology Letters, 2003
The four-wave mixing (FWM) process in single-mode optical fibers is investigated by considering t... more The four-wave mixing (FWM) process in single-mode optical fibers is investigated by considering that a zero-dispersion wavelength varies along the length of the fiber link, which is represented as a series of segments with different lengths, propagation constants, and zero-dispersion wavelengths. The results indicate that new optical frequencies are efficiently generated for particular combinations of the input-signal wavelengths, even when the phase-matching condition is not fully met.