359 research outputs found
All-optical technique for modulation format conversion from on-off-keying to alternate-mark-inversion
We propose and numerically investigate for the first time a novel all-optical on-off-keying to alternate-mark-inversion modulation format converter operating at 40 Gbps employing a semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer (MZI). Wedemonstrate that this SOA-MZI operates as a pulse subtractor, and in the absence of patterning will produce perfectly phase inverted pulses regardless of the individual SOA phase excursions. We use a comprehensive computer model to illustrate the impact of patterning on the output phase modulation which is quantified through the definition of the phase compression factor
Next generation passive optical networks using frequency division multiplexing
We discuss the use of frequency division
multiplexing in next-generation PON. We start by discussing
pros and cons of FDMA compared to traditional TDMA
approach, then present the latest results from the EU project
FABULOUS
Modulation format comparison in PMD-Impaired 40Gbps systems
Tese de mestrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200
Microwave vs optical crosslink study
The intersatellite links (ISL's) at geostationary orbit is currently a missing link in commercial satellite services. Prior studies have found that potential application of ISL's to domestic, regional, and global satellites will provide more cost-effective services than the non-ISL's systems (i.e., multiple-hop systems). In addition, ISL's can improve and expand the existing satellite services in several aspects. For example, ISL's can conserve the scarce spectrum allocated for fixed satellite services (FSS) by avoiding multiple hopping of the relay stations. ISL's can also conserve prime orbit slot by effectively expanding the geostationary arc. As a result of the coverage extension by using ISL's more users will have direct access to the satellite network, thus providing reduced signal propagation delay and improved signal quality. Given the potential benefits of ISL's system, it is of interest to determine the appropriate implementations for some potential ISL architectures. Summary of the selected ISL network architecture as supplied by NASA are listed. The projected high data rate requirements (greater than 400 Mbps) suggest that high frequency RF or optical implementations are natural approaches. Both RF and optical systems have their own merits and weaknesses which make the choice between them dependent on the specific application. Due to its relatively mature technology base, the implementation risk associated with RF (at least 32 GHz) is lower than that of the optical ISL's. However, the relatively large antenna size required by RF ISL's payload may cause real-estate problems on the host spacecraft. In addition, because of the frequency sharing (for duplex multiple channels communications) within the limited bandwidth allocated, RF ISL's are more susceptible to inter-system and inter-channel interferences. On the other hand, optical ISL's can offer interference-free transmission and compact sized payload. However, the extremely narrow beam widths (on the order of 10 micro-rad) associated with optical ISL's impose very stringent pointing, acquisition, and tracking requirements on the system. Even if the RF and optical systems are considered separately, questions still remain as to selection of RF frequency, direct versus coherent optical detection, etc. in implementing an ISL for a particular network architecture. These and other issues are studied
Modulação e conversão de formatos óticos avançados
Doutoramento em Engenharia ElectrotécnicaOver the years, the increased search and exchange of information lead to an
increase of traffic intensity in todays optical communication networks. Coherent
communications, using the amplitude and phase of the signal, reappears as
one of the transmission techniques to increase the spectral efficiency and
throughput of optical channels.
In this context, this work present a study on format conversion of modulated
signals using MZI-SOAs, based exclusively on all- optical techniques through
wavelength conversion. This approach, when applied in interconnection nodes
between optical networks with different bit rates and modulation formats, allow
a better efficiency and scalability of the network.
We start with an experimental characterization of the static and dynamic
properties of the MZI-SOA. Then, we propose a semi-analytical model to
describe the evolution of phase and amplitude at the output of the MZI-SOA.
The model’s coefficients are obtained using a multi-objective genetic algorithm.
We validate the model experimentally, by exploring the dependency of the
optical signal with the operational parameters of the MZI-SOA.
We also propose an all-optical technique for the conversion of amplitude
modulation signals to a continuous phase modulation format. Finally, we study
the potential of MZI-SOAs for the conversion of amplitude signals to QPSK and
QAM signals. We show the dependency of the conversion process with the
operational parameters deviation from the optimal values. The technique is
experimentally validated for QPSK modulation.Nos últimos anos, a crescente procura e troca de informação tem levado ao
aumento de tráfego nas redes de comunicação óticas atuais. As comunicações
coerentes, com recurso à amplitude e fase do sinal, ressurgem como uma das
técnicas de transmissão capazes de aumentar a eficiência espectral e o
rendimento dos canais óticos. Nesse âmbito, este trabalho apresenta um
estudo sobre a conversão de formatos de modulação de sinais, usando
técnicas exclusivamente no domínio ótico, através de conversão de
comprimento de onda, com base no MZI-SOA. Esta técnica, aplicada em nós
óticos que interligam redes óticas com débitos binários distintos, permite uma
maior escalabilidade e eficiência da rede.
A tese começa por apresentar uma caracterização experimental detalhada das
propriedades estáticas e dinâmicas do MZI-SOA. É depois proposto um modelo
semi-analítico que descreve a evolução da amplitude e fase do sinal ótico à
saída do MZI-SOA. Os coeficientes do modelo são obtidos recorrendo a um
algoritmo genético multiobjectivo. O modelo é validado experimentalmente,
explorando a dependência do sinal ótico com os parâmetros operacionais do
MZI- SOA.
Segue-se a proposta de uma técnica de conversão de formato de modulação
de amplitude para modulação de fase contínua. Finalmente, é feito um estudo
das potencialidades do MZI-SOA para conversão de formato de modulação de
amplitude para modulação QPSK e QAM. Mostra-se a dependência da
constelação do sinal com o desvio dos parâmetros operacionais, em torno do
valor ótimo. A técnica é validada experimentalmente para modulação QPSK
Advanced Technique and Future Perspective for Next Generation Optical Fiber Communications
Optical fiber communication industry has gained unprecedented opportunities and achieved rapid progress in recent years. However, with the increase of data transmission volume and the enhancement of transmission demand, the optical communication field still needs to be upgraded to better meet the challenges in the future development. Artificial intelligence technology in optical communication and optical network is still in its infancy, but the existing achievements show great application potential. In the future, with the further development of artificial intelligence technology, AI algorithms combining channel characteristics and physical properties will shine in optical communication. This reprint introduces some recent advances in optical fiber communication and optical network, and provides alternative directions for the development of the next generation optical fiber communication technology
- …