Depuis quelques années, les réseaux optiques sur puce (ONoC) sont devenus une solution intéressante pour surpasser les limitations des interconnexions électriques, compte tenu de leurs caractéristiques attractives concernant la consommation d’énergie, le délai de transfert et la bande passante. Cependant, les éléments optiques nécessaires pour définir un tel réseau souffrent d’imperfections qui introduisent des pertes durant les communications. De plus, l'utilisation de la technique de multiplexage en longueurs d'ondes (WDM) permet d'augmenter les performances, mais introduit de nouvelles pertes et de la diaphonie entre les longueurs d'ondes, ce qui a pour effet de réduire le rapport signal sur bruit et donc la qualité de la communication. Les contributions présentées dans ce manuscrit adressent cette problématique d’amélioration de performance des liens optiques dans un ONoC. Pour cela, nous proposons tout d’abord un modèle analytique des pertes et de la diaphonie dans un réseau optique sur puce WDM. Nous proposons ensuite une méthodologie pour améliorer les performances globales du système s'appuyant sur l'utilisation de codes correcteurs d'erreurs. Nous présentons deux types de codes, le premier(Hamming) est d'une complexité d'implémentation faible alors que le second(Reed-Solomon) est plus complexe, mais offre un meilleur taux de correction. Nous avons implémenté des blocs matériels supportant ces corrections d'erreurs avec une technologie 28nm FDSOI. Finalement, nous proposons la définition d'une interface complète entre le domaine électrique et le domaine optique permettant d'allouer les longueurs d'ondes, de coder l'information, de sérialiser le flux de données et de contrôler le driver du laser pour obtenir la modulation à la puissance optique souhaitée. / Electrical Network-on-Chip (ENoC) has long been considered as the de facto technology for interconnects in multiprocessor systems-on-chip (MPSoCs). However, with the increase of the number of cores integrated on a single chip, ENoCs are less and less suitable to adapt the bandwidth and latency requirements of nowadays complex and highly-parallel applications. In recent years, due to power consumption constraint, low latency, and high data bandwidth requirements, optical interconnects became an interesting solution to overcome these limitations. Indeed, Optical Networks on Chip (ONoC) are based on waveguides which drive optical signals from source to destination with very low latency. Unfortunately, the optical devices used to built ONoCs suffer from some imperfections which introduce losses during communications. These losses (crosstalk noises and optical losses) are very important factors which impact the energy efficiency and the performance of the system. Furthermore, Wavelength Division Multiplexing (WDM) technology can help the designer to improve ONoC performance, especially the bandwidth and the latency. However, using the WDM technology leads to introduce new losses and crosstalk noises which negatively impact the Signal to Noise Ratio (SNR) and Bit Error Rate (BER). In detail, this results in higher BER and increases power consumption, which therefore reduces the energy efficiency of the optical interconnects. The contributions presented in this manuscript address these issues. For that, we first model and analyze the optical losses and crosstalk in WDM based ONoC. The model can provide an analytical evaluation of the worst case of loss and crosstalk with different parameters for optical ring network-on-chip. Based on this model, we propose a methodology to improve the performance and then to reduce the power consumption of optical interconnects relying on the use of forward error correction (FEC). We present two case studies of lightweight FEC with low implementation complexity and high error-correction performance under 28nm Fully-Depleted Silicon-On-Insulator (FDSOI) technology. The results demonstrate the advantages of using FEC on the optical interconnect in the context of the CHAMELEON ONoC. Secondly, we propose a complete design of Optical Network Interface (ONI) which is composed of data flow allocation, integrated FECs, data serialization/deserialization, and control of the laser driver. The details of these different elements are presented in this manuscript. Relying on this network interface, an allocation management to improve energy efficiency can be supported at runtime depending on the application demands. This runtime management of energy vs. performance can be integrated into the ONI manager through configuration manager located in each ONI. Finally, the design of an ONoC configuration sequencer (OCS), located at the center of the optical layer, is presented. By using the ONI manager, the OCS can configure ONoC at runtime according to the application performance and energy requirements.
| Identifer | oai:union.ndltd.org:theses.fr/2018REN1S076 |
| Date | 13 December 2018 |
| Creators | Pham, Van Dung |
| Contributors | Rennes 1, Sentieys, Olivier, Chillet, Daniel |
| Source Sets | Dépôt national des thèses électroniques françaises |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation, Text |
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