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Abstract

Optics represents an elegant and reliable solution to generate high spectral purity microwave signals, especially the approach using the optoelectronic oscillator (OEO). The spectral purity of these sources is very important for space and military applications and also for time and frequency domain metrology. During this thesis, we have fabricated and studied many types of resonator based OEO in order to optimize the system phase noise. We have especially investigated an original approach using a passive fiber ring resonator (FRR). This resonator type can feature optical quality factors higher than 109 when only few meters of optical fibers are used (L ~ 10 m) and it can be easily integrated in a planar setup. Moreover, we have performed an important work on 3D WGM resonators based oscillators. In the FRR based OEO, spectacular progresses have been achieved thanks to a good understanding of the system intrinsic noise phenomena. Actually, we have found that the most important noise parameters were the laser FM and AM noise conversion into RF phase noise by means of different nonlinearities in the system (like the photodiode nonlinearity), but also by the generation of nonlinear optical effects inside the resonator. By controlling these effects, we have been able to reduce the OEO phase noise level and to reach a -128 dBc/Hz noise level at 10 kHz offset frequency from a 10.2 GHz carrier. This has been achieved using an OEO based on a 100m-long passive FRR, which has been optimized and immunized against different nonlinear optical effects.

Résumé

L'optique constitue aujourd'hui une solution performante pour la réalisation de sources très pures en hyperfréquences, en particulier grâce à l'approche de l'oscillateur électro-optique (OEO). La pureté spectrale de ces sources est essentielle pour les applications spatiales, militaires et pour la métrologie du temps et des fréquences. Durant cette thèse, nous avons réalisé et étudié différents types d'OEO à résonateur optique en vue d'optimiser le bruit de phase de ce système. Nous avons en particulier orienté nos travaux vers une approche originale utilisant un anneau résonant fibré (ARF) passif. Ce type de résonateur présente en effet des coefficients de qualité optiques supérieurs à 109 pour des longueurs de fibre restant relativement faibles (L ~ 10 m) et facilement intégrables dans un support planaire. En parallèle, nous avons mené un travail important sur les oscillateurs à base de résonateurs optiques 3D. Concernant l'OEO à ARF, des progrès spectaculaires ont pu être obtenus grâce à une meilleure compréhension des phénomènes de bruit intrinsèques à ce système. Les deux types de bruit prépondérants étaient la conversion du bruit du laser (FM et AM) en bruit de phase RF par différentes non-linéarités (dont la photodiode) et le déclenchement d'effets non-linéaires optiques à l'intérieur du résonateur. Le contrôle de ces effets a permis en particulier d'éliminer des remontées importantes de bruit sur le spectre de l'oscillateur, et d'atteindre un niveau de bruit de phase de -128 dBc/Hz à 10 kHz de la porteuse à 10.2 GHz en utilisant un OEO à base d'un ARF passif de 100 mètres de longueur, optimisé et immunisé contre les effets non-linéaires optiques.

Mots-Clés / Keywords

High-Q optical resonator; Microwave photonics; Opto-Electronic Oscillator (OEO); Phase noise; Nonlinear optics; Résonateur optique à fort Q; Opto-microonde; Oscillateur Electro-Optique (OEO); Bruit de phase; Optique non-linéaire;

Abstract

Optoelectronic oscillators based on high Q optical resonators are presented in this paper. These oscillators use a Pound-Drever-Hall laser stabilization technique and two different types of resonators: fiber ring and monocrystalline disk resonators. Noise processes in the oscillators are discussed, particularly the influence of the laser noise conversion and nonlinear optical scattering noise. A modeling approach using CAD software is also proposed.

Abstract

We introduce an efficient technique to optically generate millimeter-wave sources. The technique is based on the frequency multiplication concept using high order harmonics, generated by a Mach-Zehnder modulator, combined with the Brillouin selective side band amplification process in a high Q fiber ring resonator. We demonstrate the generation of a low phase noise 65.2 GHz signal with a power level 15 dB higher than the power level usually obtained using classical frequency multiplication.

Abstract

Theoretical and experimental optimization studies are presented in this paper, where the aim is to improve the phase noise of an optoelectronic oscillator based on a passive fiber ring resonator. Our experimental results demonstrate a significant reduction in the phase noise of the final optimized system, which is also compared to the best existing oscillator of the same type, an active cavity based coupled optoelectronic oscillator.

Abstract

Various fiber optics links are evaluated for the transmission of OCXO signals on relatively short distances (1 m to 1 km). The case of VCSEL lasers is compared to the case of the more classical DFB laser. The DFB is still the best device, particularly in terms of signal to noise ratio, but single-mode VCSELs are becoming interesting as a low cost alternative to this device.

Abstract

The main parameters of a local oscillator distribution in the millimeter wave range are described. The link is based on optical frequency multiplication taking benefit of the modulator nonlinearity. It is modeled using an original CAD approach. Then, various practical solutions are compared and their phase noise floor is measured.