Etude en bruit de systèmes optiques hyperfréquences. Modélisation, caractérisation et application à la métrologie en bruit de phase et à la génération de fréquence

Les composants optoélectroniques sont de plus en plus utilisés dans les systèmes micro-ondes. Les liaisons par fibres optiques, permettent par exemple une réduction significative de la taille et de la masse des systèmes de distribution de signaux à bord des systèmes embarqués (avion, satellite, radar,...). Cependant, les performances de ces systèmes dépendent des performances des dispositifs utilisés pour les conversions électrique/optique et optique/électrique, de la technique de modulation optique choisie, des amplificateurs micro-ondes utilisés, de la qualité de la fibre optique et, finalement, de la topologie choisie pour réaliser le système entier. Ceci explique l'importance de développer une approche de modélisation efficace pour ces systèmes. Cette thèse nous a permis de développer une telle approche basée sur un logiciel de simulation de circuits hyperfréquences, comprenant différentes méthodes d'analyse des systèmes non-linéaires (dont la balance harmonique) et du bruit dans ces systèmes (conversion de bruit entre les harmoniques). L'originalité de ce travail consiste en l'utilisation de ce logiciel pour simuler des composants optoélectroniques, qui sont décrits par des équivalents électriques ou mathématiques. Grâce à cette étude, nous avons pu modéliser dans un premier temps une liaison optique utilisant un modulateur de Mach-Zehnder et incluant les différentes composantes de bruit du système. Un modèle est également proposé pour un discriminateur de fréquence micro-ondes à ligne à retard optique et enfin pour un discriminateur de fréquence optique. Sur la base de cette étude, un discriminateur de fréquence micro-onde utilisant une ligne à retard optique de plusieurs kilomètres a été conçu et réalisé. Ce système présente des performances en bruit de phase à l'état de l'art.Optical devices are more and more used in microwave systems, taking benefit of the low losses of optical fibers, of their small size and their immunity to electrical parasitic signals. An example of these systems is the microwave optical oscillator, either based on optical resonators or delay lines, which can deliver ultra high spectral purity signals. However, the performance of these systems is dependent on the performance of the devices used for the electrical to optical or optical to electrical conversions, the chosen optical modulation technique, the necessary microwave amplifiers, the devices biasing circuits, the quality of the optical fiber and, above all, the topology chosen to build the whole system. It is thus important to be able to compute the system phase noise using an appropriate modelling approach. This thesis allowed us to develop such approach using specific microwave circuit design software: Agilent ADS. This software has been designed in the 1990s in order to take into account the frequency conversion phenomena between the noise sidebands around the different harmonics of the RF signal (including DC). This software may be used to simulate the microwave parts of a microwave optical system. However, it generally does not include any specific model for the optical devices involved in these systems. A solution to this problem is to find a representation of these devices which can be implemented in the microwave simulator, using either an equivalent electrical circuit or a mathematical model. Finally, a Mach-Zehnder modulator based optical link and its noise performance is successfully described. A model is proposed for an optical delay line microwave frequency discriminator and also for an optical discriminator. Thanks to this study, an optical delay line microwave frequency discriminator is designed and realized. The phase noise performance of this system corresponds to the state of the art

Optimization and evaluation in space conditions of multi-GHz optical modulators

Among the different optical modulator technologies available such as polymer, III-V semiconductors, Silicon, the well-known Lithium Niobate (LN) offers the best trade-off in terms of performances, ease of use, and power handling capability [1-9]. The LN technology is still widely deployed within the current high data rate fibre optic communications networks. This technology is also the most mature and guarantees the reliability which is required for space applications [9].In or der to fulfil the target specifications of opto-microwave payloads, an optimization of the design of a Mach-Zehnder (MZ) modulator working at the 1500nm telecom wavelength was performed in the frame of the ESA-ARTES "Multi GigaHertz Optical Modulator" (MGOM) project in order to reach ultra-low optical insertion loss and low effective driving voltage in the Ka band. The selected modulator configuration was the X-cut crystal orientation, associated to high stability Titanium in-diffusion process for the optical waveguide. Starting from an initial modulator configuration exhibiting 9 V drive voltage @ 30 GHz, a complete redesign of the coplanar microwave electrodes was carried out in order to reach a 6 V drive voltage @ 30GHz version. This redesign was associated to an optimization of the interaction between the optical waveguide and the electrodes. Following the optimisation steps, an evaluation program was applied on a lot of 8 identical modulators. A full characterisation was carried out to compare performances, showing small variations between the initial and final functional characteristics. In parallel, two similar modulators were submitted to both gamma (10-100 krad) and proton irradiation (10.109 p/cm²) with minor performance degradation

Étude en bruit de systèmes optiques hyperfréquences modélisation, caractérisation et application à la métrologie en bruit de phase et à la génération de fréquence

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Approche CAO de systèmes optiques-hyperfréquences incluant les performances en bruit

4 pagesNational audienceIl est important de pouvoir modéliser les performances de liaisons et systèmes optiques hyperfréquences, dont leurs performances en termes de bruit de phase, et de comparer ces résultats avec ceux obtenus analytiquement et expérimentalement. Nous avons donc tenté une approche de modélisation utilisant un logiciel CAO : Agilent ADS. Il s'agit d'un logiciel de simulation de circuit hyperfréquences relativement complet, comprenant différentes méthodes du bruit (incluant le bruit de phase). La particularité ici, consiste en l'utilisation de ce logiciel pour simuler des composants optoélectroniques, qui sont décrits par des équivalents électriques ou mathématiques

MODELISATION DE SYSTEMES OPTIQUES-HYPERFREQUENCES A L'AIDE D'UN LOGICIEL DE CAO MICRO-ONDE

National audienceIl est important de pouvoir modéliser les performances de liaisons et systèmes optiques hyperfréquences, dont leurs performances en termes de bruit de phase, et de comparer ces résultats avec ceux obtenus analytiquement et expérimentalement. Nous avons donc tenté une approche de modélisation utilisant un logiciel CAO : Agilent ADS. Il s'agit d'un logiciel de simulation de circuits hyperfréquences relativement complet, comprenant différentes méthodes d'analyse du bruit incluant le bruit de phase dans les circuits non-linéaires. La particularité ici, consiste en l'utilisation de ce logiciel pour simuler des composants optoélectroniques, qui sont décrits par des équivalents électriques ou mathématiques

Optimization of a microwave frequency discriminator based on an optical delay line

International audienceA microwave frequency discriminator based on an optical delay line is studied. This system features a noise floor below -150 dBc/Hz at 10 kHz offset. The noise mechanisms are studied in order to determine the main noise contributors

Evaluation de différentes techniques de mesure du bruit de phase de sources optiques et hyperfréquences utilisant une ligne à retard optique

5 pagesInternational audienceThe unique property of the ultra low losses of optical fiber can be used in the field of metrology to reach large delays, which are equivalent to ultra high quality factors. It is thus possible to realize, with a fiber spool, passive frequency references which can be used to characterize frequency sources of different type : microwave frequency sources and optical frequency sources. This paper describes two different benches, one in the microwave domain and the other one in the optical domain, which are based on optical fiber delay lines. The first bench is used to measure the phase noise of very high spectral purity microwave sources. The other one is dedicated to the measurement of the frequency fluctuations of ultra high spectral purity infrared lasers

CAD OF MICROWAVE OPTICAL SYSTEMS FOR TIME&FREQUENCY APPLICATIONS

International audienceOptical devices are more and more involved in time and frequency applications. They may be used for frequency reference signal distribution in a system, taking benefit of the low losses of the optical fibers, and of their small size and their immunity to electrical parasitic signals. They may also be used to realize high quality resonators and delay lines, leading to equivalent Q factors which are difficult to reach with classical RF or microwave techniques. It is important to be able to compute microwave-optical links and systems. Specially, phase noise system. This paper gives an overview of various approaches which can be used to describe an optical device with an equivalent electrical circuit, or simply with a mathematical model, and to include this model in the chosen CAD tool. We have worked with Agilent ADS microwave simulation software

Optical techniques for microwave frequency stabilization : resonant versus delay line approaches and related modelling problems

International audienceOptical techniques for microwave oscillators stabilization or microwave sources phase noise measurement are discussed. The advantage in terms of Q factor of optical resonant devices goes with increased difficulties in the system stabilization. System modelling is also complex, because of the interaction of noise sources around three different frequencies : optical, microwave and baseband

High-Q Optical Resonators for Laser Stabilization in Microwave Photonics Oscillators

International audienceHigh-Q optical resonators are interesting for microwave oscillators and laser stabilization. We present whispering gallery modes resonators and resonant fibre loops with measured optical quality factors higher than 10^9, and an application