A fibra óptica apresenta características que favorecem a propagação de sinais eletromagnéticos de um ponto a outro, quando comparada a outros guias de onda. O desempenho máximo da fibra óptica enquanto guia de onda depende da escolha apropriada da topologia de rede, tanto em seu aspecto físico quanto lógico. Na medida em que topologias de rede mais eficientes são apresentadas, abrem-se possibilidades de melhorias para os enlaces já instalados. Após estudo e avaliação técnica criteriosa das características de tráfego da rede, é possível verificar se a topologia física utilizada é a mais indicada e propor alterações que conduzirão à melhoria do desempenho de comunicação. Neste contexto, este trabalho apresenta importantes avanços técnicos para a interconexão dos diversos campi da Universidade Federal do Pampa (UNIPAMPA). Estes avanços podem ser alcançados através da adoção da topologia física mais apropriada a interligar os dez campi da instituição, situados ao longo da fronteira oeste do Rio Grande do Sul, além da reitoria, distribuída em dois endereços na cidade de Bagé. A topologia proposta é do tipo malha e é avaliada em termos orçamento de potência (alcance do sinal), orçamento de tempo (sensibilidade à dispersão) e de custo. Os custos referentes aos componentes da camada física são examinados para três diferentes propostas. A rede proposta ostenta vantagens como uma maior robustez a falhas devido a rompimentos ou ao congestionamento da rede, também permite oferecer uma maior qualidade de serviço em função da redução da latência na rede, ou seja, da redução do tempo necessário à comunicação. Este trabalho poderá ser utilizado para o embasamento técnico, auxiliando em decisões para futuras evoluções na infraestrutura óptica da UNIPAMPA.

Optical communications are widely used in our daily lives for data transmission and offer high quality and efficiency. However, it is necessary to constantly evolve the technology and infrastructure to meet the needs and expectations of consumers, such as high definition videos, virtual reality, and 5G mobile networks that require higher transmission rates and wider bandwidths. This presents new challenges for PON (Passive Optical Network) based technologies, which are currently the most commonly used in access networks, with advantages of efficiency, transmission rate and implementation cost. The integration of optical components on a single chip (Integrated Optical Circuits or PIC) is essential for the evolution of PON technology as it allows for reduction of energy consumption and complexity. This document addresses the development of new data transmission standards, namely those that present rates of 50 Gbps. Additionally, the implementation of 50 Gbps systems was studied, including simulations of different modulation and transmission technologies, such as EML (Externally Modulated Laser) and DML (Directly Modulated Laser), using O-band wavelength. The objective is to analyze the advantages and limitations of each technology. Additionally, experimental tests and simulations with 25G-PON technology were performed to characterize and evaluate the performance of SFP28 transceivers. Finally, the design and implementation of a PIC architecture with 50Gbps support was also developed, using an EML.

During the last few years there has been a significative increase of the study and development of autonomous driving systems, in order to have a lower rate of car accidents in the future. One of the main functions necessary for a good performance of this type of systems is the detection and distance estimation of a potential obstacle. This can be achieved through the use of LIDAR (Light Detection and Ranging) technology, within which the most used application is the pulsed LIDAR, for which a direct measurement of the time-of-flight of pulses, which are transmitted by a laser, reflected at an obstacle and captured by a receiver, is done. However, the cost and complexity of this type of implementation are still too high. Throughout this thesis, another type of LIDAR technique known as AMCW (Amplitude-modulated Continuous Wave) was then explored, for which continuous signals are amplitude-modulated and for which a good precision was obtained for the estimation of distances of an obstacle up to 300 m. This technique introduces the possibility of a reduction in cost and complexity of this type of system. Different ideal and non-ideal cases were simulated for two estimation methods e for different types of waveforms, in order to understand which parameters and working conditions enable the optimization of the system. Another great focus of this thesis was the influence of the presence of interferences, originated from other LIDARs, on the estimation methods. From the obtained results, it was observed that even for scenarios with the presence of various interferences, the system is capable of making estimations with an acceptable absolute error. Lastly, the possibility of implementing a communication system in cooperation with the studied estimation system without losses in estimation quality, was tested. It was concluded that this implementation is possible, guaranteed that some conditions relative to the transmitted signals are respected.

Traditional coherent (COH) transceivers allow encoding of information in both quadratures and the two orthogonal polarizations of the electric field. Nevertheless, such transceivers used today are based on the intradyne scheme, which requires two 90o optical hybrids and four pairs of balanced photodetectors for dual-polarization transmission systems, making its overall cost unattractive for short-reach applications. Therefore, SSB methods with DD reception, commonly referred to as self-coherent (SCOH) transceivers, can be employed as a cost-effective alternative to the traditional COH transceivers. Nevertheless, the performance of SSB systems is severely degraded. This work provides a novel SCOH transceiver architecture with improved performance for short-reach applications. In particular, the development of phase reconstruction digital signal processing (DSP) techniques, the development of other DSP subsystems that relax the hardware requirement, and their performance optimization are the main highlights of this research. The fundamental principle of the proposed transceiver is based on the reception of the signal that satisfies the minimum phase condition upon DD. To reconstruct the missing phase information imposed by DD, a novel DCValue method exploring the SSB and the DC-Value properties of the minimum phase signal is developed in this Ph.D. study. The DC-Value method facilitates the phase reconstruction process at the Nyquist sampling rate and requires a low intensity pilot signal. Also, the experimental validation of the DC-Value method was successfully carried out for short-reach optical networks. Additionally, an extensive study was performed on the DC-Value method to optimize the system performance. In the optimization process, it was found that the estimation of the CCF is an important parameter to exploit all advantages of the DC-Value method. A novel CCF estimation technique was proposed. Further, the performance of the DC-Value method is optimized employing the rate-adaptive probabilistic constellation shaping.

This article analyzes the transient effect in pump-reflecting Raman fiber amplifiers. In order to better understand the impact of reflecting the unused pump power in the amplifier behavior, several scenarios are investigated. Results show that this pumping scheme has a worse response to dynamic channel add/drop. However, a pump-controlled gain-locked system is proposed that is able to mitigate the amplifier transient response. Following this approach, an efficient low-cost Raman fiber amplifier suitable for dynamic optical networks is obtained.

In this letter we will evaluate the performance degradation of a 40 km high-speed (40 Gb/s) optical System, induced by optical fiber variations of the chromatic dispersion induced by temperature changes. The chromatic dispersion temperature sensitivity will be estimated based on the signal quality parameters.

The constant emergence of new products and services through communication networks, namely the Internet, leads to the demand for technology capable of providing these services with increasing speeds and bandwidth. Nowadays, the technology suitable to provide these features is communication through an optical fiber (optical communications). This technology is applied by PON networks, in which architectures distribute optical fiber from the central office (OLT) through the final user (ONT or ONU). It is in the context of these networks that arise the integrated optical applications for implementation of these structures (OLTs and ONTs) for data transmission and reception with reduced energy consumption, complexity as well as size. Therefore, these chips pretend to include, in one single copy, several optical components multiplying its functionalities in very reduced sizes and, for power consume reduction, using mostly passive elements. This dissertation intends to contribute with new solutions development for implementation of new structures capable to meet the user needs, with a development of a new architecture for implementing a PIC transmitter to be integrated on the client-side at the ONT. The optoelectronic solution should be capable of address 40 GBit/s of data rate and, for that, it should also be evaluated an implementation method to apply channel multiplexing to the system that, at the same time that it allows the 40 Gbit/s bit rate output, presents low additional loss values to the system. The proposal architecture should also ensure an 8 dBm of minimum output optical power. Besides, the final chip must be compliant with NG-PON2 network requirements

The current society is increasingly dependent on communication services, requiring better and faster connections, predicting in a near future connections in the order of hundreds of Gbit/s. During the data transmissions, the increase of speed reflects an increase of the error ratio due to factors such as noise, reductions of signal or jitter, which for low speed these were not emphasized so much. This project involves the development of a BER test system for both continuous and Burst mode of the transmission, demonstrating the viability of communication over the next-generation technology, NG-PON2, which uses high transmission rates (10 Gbit/s). For this purpose, an FPGA architecture was implemented that allows for long distances in the optical network, high transmission rates. This choice reflects a more economical alternative in relation to commercial equipment and has several advantages, such as the flexibility to reprogram and prepare the architecture according to the needs of the user. To achieve the proposed requirements, the project was divided into three parts. In the first part an architecture was developed that allows to obtain the error rate during a continuous mode transmission. In order to obtain the real-time viability of the communication referred and to have control over the system, an interface was developed between the computer and the FPGA to change certain characteristics of the communication channel. This is the second part of the project. The last part of the project has an architecture similar to the previous one, that is, instead of the transmission to be done in continuous mode, it is performed in mode Burst, being this the requirement with more interest to the technology NG-PON2. Finally, proof of concept was performed through an optical network provided by the company PICadvanced that allowed the validation of the different parts of the project. These validations will allow the development of new modules that will later contribute to the main project that is under development in the company PICadvanced, which aims at the construction of an automatic calibration board for the XFP transceivers.

Multi-subcarrier optical systems have recently attracted the attention of the scienti c and industrial communities, owing to their inherent advantages in terms of ber propagation performance as well as their implementation complexity, when compared with legacy single-carrier systems. With the imminent introduction of next-generation transceivers supporting aggregate symbol-rates beyond 100 Gbaud, the achievable gains provided by multisubcarrier modulation are becoming increasingly more important, thereby attracting the attention of several leader optical manufacturers, which are now including this technology in their portfolio. However, the transition from single-carrier to multi-subcarrier modulation still requires signi cant optimization of digital signal processing subsystems, in order to maximize the inherent potential of subcarrier multiplexing. In this thesis, techniques for carrier phase estimation are explored. The penalty associated with the usage of the methods used in single-carrier systems when changing to a multi-subcarrier system is quantitatively studied and the need for a change in such methods is evidenced. Several jointly processing carrier phase estimation approaches are employed to improve the performance of phase recovery algorithms, resulting in an improvement in the power requirements for multi-subcarrier systems. In particular, a novel approach to carrier phase estimation is developed and assessed. This new method increases the tolerance of the system to chromatic dispersion and makes viable the usage of multi-subcarrier systems with a high number of subcarriers, highly outperforming any other carrier phase estimation approach for such systems. Finally, a novel low-complexity implementation of a digital monitoring system is suggested. It is capable of measuring the laser line width of the transmitter and local oscillators lasers. This implementation is only made possible by the nature associated with the novel algorithm presented.

In this work, we review the most important achievements of INESC TEC related to the properties and applications of arc-induced long-period fiber gratings. The polarization dependence loss, the spectral behavior at temperatures ranging from cryogenic up to 1200 C and under exposure to ultraviolet and gamma radiation is described. The dependence of gratings sensitivity on the fabrication parameters is discussed. Several applications in optical communications and sensing domains are referred.