Orientadores: Aldário Chrestani Bordonalli, Júlio César Rodrigues Fernandes de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-24T05:17:21Z (GMT). No. of bitstreams: 1 Diniz_JulioCesarMedeiros_M.pdf: 3463779 bytes, checksum: 7779aef72110b0e57aedeef25fc53b07 (MD5) Previous issue date: 2013 / Resumo: Sistemas de comunicações ópticas coerentes digitais permitem a utilização de formatos de modulação que carregam informação através de fase, amplitude e polarização do sinal óptico. Com o processamento digital dos sinais ópticos, é possível compensar as distorções inerentes à transmissão óptica, bem como realizar o sincronismo entre transmissor e receptor. Assim, junto ao avanço da eletrônica digital, a transmissão e recepção de sinais a centenas de gigabits por segundo se torna possível. Dentro desse cenário, os métodos comuns para a estimação de fase da portadora que chega ao receptor possuem baixa tolerância à dessintonia em frequência entre a portadora transmitida e o laser oscilador local. Nesta dissertação, é proposto e experimentalmente demonstrado um método de estimação de desvios de frequência de alimentação direta, com amplo alcance de estimação, eficiente, no ponto de vista de hardware, e compatível com os requisitos definidos pelo Fórum de Interconexões Ópticas (OIF ¿ Optical Internetworking Forum). Resultados obtidos experimentalmente mostram que o método proposto possui alta tolerância à assimetria espectral causada por filtragens no sinal / Abstract: Digital coherent optical systems allow the use of modulation formats that carry information through optical signal phase, amplitude and polarization. With digital processing of optical signals it is possible to compensate for distortions associated with optical transmission, as well as to perform timing and carrier synchronization. Thus, by also taking into account the current high speed electronic progress, transmission and reception of signals at hundreds gigabits per second has became possible. In this scenario, common carrier phase estimation methods have low tolerance to frequency offsets between transmitted carrier and local oscillator laser. This dissertation proposes and experimentally demonstrates a hardware-efficient, feed-forward, wide-range frequency offset estimator, compliant with Optical Internetworking Forum (OIF) requirements. Experimental results show that this method has high tolerance to the spectrum asymmetry caused by signal filtering / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Orientador: Evandro Conforti / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-21T04:49:45Z (GMT). No. of bitstreams: 1 Rocha_Peterson_M.pdf: 5254230 bytes, checksum: 811832dc531fcd6bcc9edf29f71bf219 (MD5) Previous issue date: 2012 / Resumo: Modulações ópticas avançadas como DQPSK e QAM tem sido escolhidas por serem formatos multiniveis (dois bits ou mais por símbolo), aumentando a eficiência espectral de sistemas ópticos. Entretanto, o amplificador óptico a semicondutor (SOA) indicado principalmente para aplicações de media distancia (da ordem de 20 km), pode degradar o sinal DQPSK e QAM. Sistemas de fase modulada (como o DQPSK) são afetados principalmente por SPM e XPM, devido ao ruído de fase não-linear adicionado a fase óptica do sinal. Visando analisar estes problemas, apresenta-se um estudo sobre os sinais NRZ-DQPSK e 16-QAM amplificados pelo SOA, bem como outros fatores que degradam tais sistemas, através de simulações com os softwares comerciais OptiSystem e VPItransmissionMaker. Nas simulações, resultados foram obtidos estando em acordo com a teoria e em acordo com o capitulo 3. Para o sistema DQPSK, o SOA degradou o sinal em todos cenários propostos para avaliar o sistema. O sinal NRZ-DQPSK apresentou maior penalidade quando o ganho do SOA foi de 20 dB. Efeitos não-lineares juntamente com a dispersão cromática limitam fortemente a distancia do enlace, e ao compensar a dispersão cromática no enlace com maior penalidade em 56 Gbps, o sinal NRZ-DQPSK pode trafegar por uma distancia 10 vezes maior (de 5 km para 50 km) com uma BER de 10-12. Para o sistema QAM, o sinal foi penalizado pelo SOA em todos os casos, e utilizando o SOA com ganho grampeado, os efeitos não-lineares foram minimizados, melhorando substancialmente o desempenho. Compensando a dispersão cromática e usando o SOA com ganho grampeado para o caso com maior penalidade, o sinal 16-QAM viajou a uma distancia 16 vezes maior (3 km e 50 km) / Abstract: High spectral efficiency is being achieved in modern optical fiber systems using multilevel optical modulation formats such us DQPSK and QAM, with more than one bit per symbol. However, amplifying devices such as the semiconductor optical amplifier (SOA) can degrade the DQPSK signal. In recent years SOAs have gained much attention (mainly in medium distance links, around 20 km) due to non-linear and fast switching potential applications (wavelength conversion, 3R regeneration, optical packet switching, etc.). In addition, the SOA under gain saturation further enhance deleterious nonlinear effects such as SPM, XGM, FWM, XPM. Phase modulated systems as DQPSK are affected mainly by SPM and XPM due to the nonlinear phase noise added to the controlled phase of the optical modulated signal. This work presents a study on the NRZ-DQPSK and 16-QAM signals when amplified by SOAs, analyzing the main factors degrading such systems through simulations using commercial OptiSystem and VPItransmissionMaker software. SOA showed degradation effects over DQPSK, with larger penalties to NRZ signals and optical gain over 20 dB. Non-linear effects and chromatic dispersion impose a maximum distance limit. In dispersion compensated links, 10 fold distances are achieved in relation to standard fibers (5 to 50 km) with BER= 10-12. For 16 QAM, the penalties are still high. However, gain clamped SOAs have better performance with a 16 fold distance increase (3 km to 50 km) / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Orientador: Celso de Almeida / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T08:17:41Z (GMT). No. of bitstreams: 1 Panaro_JoseSantoGuiscafre_D.pdf: 1026204 bytes, checksum: 40282f66b4b6eda29d96f913e55549ee (MD5) Previous issue date: 2005 / Resumo: O presente trabalho investiga códigos adequados para esquemas CDMA em redes de comunicação por meios ópticos como, por exemplo, fibras ópticas e redes sem fio por infravermelho. O trabalho desenvolve uma base teórica do comportamento de sistemas CDMA em canais unipolares submetidos à interferência estritamente positiva e sinalização binária, e antecipa as suas implicações. Além disso, verifica-se o desempenho de códigos unipolares apropriados para comunicação óptica propostos anteriormente, comparando-os com uma nova classe de códigos ópticos com salto temporal (OTH). Finalmente, para sistemas ópticos de múltiplo acesso por divisão de código (O-CDMA) com códigos de espalhamento ortogonais no tempo e no comprimento de onda, efetua-se uma análise de desempenho para sistemas tanto com sinalização do tipo OOK (on-off keying) quanto OOO (on-off orthogonal keying) / Abstract: This work concerns optical fiber and infrared networks using code-division multiple access techniques. A theoretical basis for the behavior of the unipolar CDMA systems under strictly positive interference and binary signaling is developed, and their consequences are predicted. In addition, the performance of unipolar codes, appropriate for optical communications is verified and compared with a new class of optical timehopping codes (OTH) proposed in this work. Finally, a performance evaluation analysis is done for O-CDMA systems using time and wavelength spreading codes, considering OOK (on-off keying) and OOO (on-off orthogonal keying) / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica

D.Ing. / Optical fibre-based devices (e.g. fibre gratings) play an important role in the optical com- munications and sensing industry. One type of fibre grating, the long-period grating (LPG), is becoming more and more popular as a simple and versatile component for a multitude of applications in optical engineering. The sensitivity of LPGs to various external perturbations and their ability to manipulate selectively light propagating in optical fibres make them well- suited to creating fibre-based devices. LPGs can be used in various applications, for example as gain equalisers for erbium-doped fibre amplifiers, as channel routers in optical add-drop multiplexers and as sensors. LPGs are typically fabricated by exposing photosensitive optical fibre to ultraviolet light. However, a variety of other techniques can be used to fabricate LPGs, including exposure to carbon dioxide (CO2) laser light. Over the years, it has become evident that CO2 laser- induced LPGs exhibit unique properties and features that can be harnessed to develop devices for important applications. It is necessary to understand the physical properties and optical characteristics of CO2 laser-induced LPGs to harness, manipulate and enhance their features. Research has been conducted on the development of an automated fabrication system that produces axially symmetric LPGs in single-mode fibre with a CO2 laser. A detailed study was undertaken on the design of uniform and non-uniform LPGs for wavelength-division multiplexing networks, as well as the characterisation of the CO2 laser beam propagating in the LPG fabrication system. These LPGs have been designed, using either analysis or syn- thesis techniques. The polarisation-dependent loss of the LPGs has also been investigated. Wavelength-selective couplers (WSCs) have been constructed using CO2 laser-induced LPGs and it was shown that these couplers were e®ective but not efficient in routing power to the output port of the tapping fibre. The physical properties, optical transmission characteris- tics, applications and other related issues of CO2 laser-induced LPGs have been investigated and satisfactory experimental results have been obtained. Areas for potential future research concerning CO2 laser-induced LPGs have been identified and discussed.

No description available.

Wavelength Division Multiplexing Passive Optical Networks (WDM PONs) offer a great solution to satisfy the increasing demand of bandwidth. In addition, it offers a higher level of data security through virtual point to point connections. A great challenge in realizing cost-effective WDM PON is the need for a transmitter at each Optical Network Unit (ONU) with a dedicated wavelength, which overloads the total cost of the system, in addition to reducing the number of available wavelengths in the system. Remodulation scheme is an ultimate solution for these problems of WDM PONs as the downstream signal itself is remodulated with upstream data which saves the need for a laser source at the ONU side. In this thesis I propose and experimentally demonstrate a novel wavelength remodulation scheme for WDM PONs that employs Differential Phase Shift Keying (DPSK) for downstream and Return to Zero DPSK (RZ-DPSK) for upstream. The use of DPSK enhanced the system with improved receiver sensitivity and RZ-DPSK improved the tolerance toward chromatic dispersion. In addition, I investigate the Backreflection (BR) penalty resulting from beat noise of BRs with upstream signal in a bidirectional WDM PON system that uses remodulation and phase modulation as a modulation format. I experimentally demonstrate the optimal conditions to operate the system and minimize the BR penalty.

No description available.

Free-space optics (FSO) is an unlicensed communication technology that uses the free space as a propagation medium to connect two communicating terminal wire- lessly [1]. It is an attractive solution to the last-mile connectivity problems in commu- nication networks, mainly when installing optical fibers is expensive or unavailable. A possible idea to increase the throughput of wireless optical links in free space is to use spatial multiplexing (SMM) [2]. Optical beam distortion due to propagation through a turbulent channel is one of the main factors limiting performance of such a system. Therefore, overcoming the effect of turbulence is a major problem for structured light optical communication in free space. Usually, this problem is approached by using adaptive optics systems and various methods of digital signal processing (DSP) on the receiver side [3–5]. Recently, an idea of optical channel pre-compensation to mit- igate inter-modal crosstalk was proposed [6] and experimentally validated [7]. Such a method, if implemented, will allow the use of entirely passive receivers or, in the case of full-duplex transmission, increase throughput. Here, the performance of a zero-forcing precoding technique to mitigate the effects of an optical turbulence in a Laguerre Gaussian mode based SMM FSO is investigated. Equally, details on a close to reality simulation of the atmospheric turbulence and beam propagation are provided.

<div>Integrated optical phased arrays (OPAs) have gained popularity for achieving beam steering with no moving parts and potential high speed and small beam divergence angle. These characteristics are crucial for applications like free-space communication and light detection and ranging (LiDAR), a key component in autonomous driving. Two main aspects that affect the performance of an integrated OPA are discussed: high power handling and large beam steering range.</div><div><br></div><div>High emission power from the OPA is desirable for long range detection applications. Silicon is broadly used in integrated OPA designs as it allows for structures with a more compact footprint. However, its power-handling capability is limited by the two-photon absorption of the material, resulting in higher loss and potential damage at high input power levels. In this work, high power delivery into free space is realized by using a silicon nitride (SiN) and silicon hybrid platform. SiN components are used to direct and split high input power into smaller portions and coupled into silicon components for a more compact emitter array.</div><div><br></div><div>In order to achieve a full 180-degree beam steering range with aliasing-free operation, the pitch of a periodic emitter array is required to be half of the operating wavelength or less. At such a small pitch, evanescent coupling between adjacent emitters causes strong crosstalk. We demonstrate the optical phased array based on uniform half-wavelength spaced grating emitter array. Two-dimensional beam confinement and a record-high aliasing-free beam steering field-of-view of 135 degrees from grating emitter are measured from a 32 channel SiN/Si hybrid OPA. Evanescent coupling between waveguides are suppressed by metamaterial-based <b>e</b>xtreme <b>ski</b>n-<b>d</b>epth (e-skid) waveguides. The e-skid waveguides utilize an alternating air-silicon multi-fin side cladding. The high index contrast of those sub-wavelength ridges provides strong anisotropy, which leads to faster decay of the evanescent wave for transverse electric (TE) input modes, thus limiting evanescent coupling between closely spaced waveguides.</div><div><br></div><div>Furthermore, we extend the concept of the half-wavelength-pitched emitter array to the design of a two-dimensional end-fire OPA. This OPA can potentially achieve 180-degree by 180-degree full-range beam steering with no grating lobes by having a half-wavelength emitter pitch in both dimensions. The design of a broadband 8 by 8 silicon photonics switch based on the half-wavelength-pitched emitter array with low path-dependent loss (PDL) is also discussed.</div>

Un lien optique basé sur un multiplex de longueurs d'onde autour de 1,55μm est une alternative intéressante pour pallier la saturation des bandes radio-fréquences classiquement utilisées et pour répondre aux besoins de liens haut débit par satellite géostationnaire de la prochaine génération de télécommunication. Compte-tenu de la puissance limitée des lasers envisagés, la divergence du faisceau doit être considérablement réduite. Par conséquent, le pointage du faisceau devient un paramètre critique. Au cours de sa propagation entre la station sol et un satellite géostationnaire, le faisceau optique est dévié et éventuellement déformé par la turbulence atmosphérique. Cela induit de fortes fluctuations du signal de télécommunication détecté, réduisant le débit disponible. Un miroir de basculement est utilisé pour pré-compenser la déviation mesurée à partir d'un faisceau provenant du satellite. Du fait de l'angle de pointage en avant entre la liaison descendante et la liaison montante, les effets de turbulence subis par les deux faisceaux sont légèrement différents, ce qui induit une erreur dans la correction.Le critère de performance de la liaison est l’intensité minimale détectable 95% du temps. Un modèle rapide, nommé WPLOT, prenant en compte les erreurs de pointage et leur évolution temporelle, est proposé pour évaluer cette intensité minimale en fonction des paramètres de la station sol et de la qualité de la correction. Les résultats obtenus avec ce modèle sont comparés avec ceux obtenus par un modèle physique mais plus couteux en temps de calcul ; le code TURANDOT. Grâce à ce modèle, une étude de sensibilité a été réalisée et a permis de proposer un dimensionnement de la station sol. Ce modèle permet également de générer des séries temporelles afin d’optimiser les codes de correction d’erreur et optimiser le débit (1Terabit/s d'ici 2025). / An optical link based on a multiplex of wavelengths at 1.55µm is foreseen to be a valuable alternative to the conventional radio-frequencies for the feeder link of the next-generation of high throughput geostationary satellite. Considering the limited power of lasers envisioned for feeder links, the beam divergence has to be dramatically reduced. Consequently, the beam pointing becomes a key issue. During its propagation between the ground station and a geostationary satellite, the optical beam is deflected and possibly distorted by atmospheric turbulence. It induces strong fluctuations of the detected telecom signal, thus reducing the capacity. A steering mirror using a measurement from a beam coming from the satellite is used to pre-compensate the deflection. Because of the point-ahead angle between the downlink and the uplink, the turbulence effects experienced by both beams are slightly different, inducing an error in the correction. The performance criteria is the minimum detectable irradiance 95% of the time. A fast model, named WPLOT, taking into account pointing errors and their temporal evolution, is proposed to evaluate the minimum irradiance as a function of the ground station parameters and quality of the correction. The model’s results are compared to those obtained with a more physical but requiring more computation power: TURANDOT. A sensitivity study has been realized and led to a sizing of a ground station. The model also enables the generation of time series in order to optimize the forward error correction codes in order to be compliant with the targeted capacity (1Terabit/s by 2025).