Optical transmitter tunable over a 65-nm wavelength range around 1550 nm for quantum key distribution

The ability to create phase-controlled pulses of light with wavelength tunability has applications spanning quantum and classical communications networks. Traditionally, optical transmitters are able to either produce phase-controlled pulses at a fixed wavelength or require a chain of bulky and expensive external modulators to convert wavelength tunable continuous-wave light into optical pulses. One technology of great interest is quantum key distribution (QKD), a technology for generating perfectly random keys at remote nodes to ensure secure communications. Environments such as data centers, where the user needs change regularly, will require adaptability in the deployment of QKD to integrate into classical optical networks. Here we propose and demonstrate an alternative quantum transmitter design consisting of a multimodal Fabry-Perot laser optically injection locked by a wavelength tunable laser. The transmitter is able to produce phase-controlled optical pulses at GHz speeds with a tunable wavelength range of >65nm centered at 1550 nm. With this transmitter, we perform proof-of-principle QKD with secure bit rates of order Mb/s

UWB FastlyTunable 0.550 GHz RF Transmitter based on Integrated Photonics

Currently, due to the 6G revolution, applications ranging from communication to sensing are experiencing an increasing and urgent need of software-defined ultra-wideband (UWB) and tunable radio frequency (RF) apparatuses with low size, weight, and power consumption (SWaP). Unfortunately, the coexistence of ultra-wideband and software-defined operation, tunability and low SWaP represents a big issue in the current RF technologies. Recently, photonic techniques have been demonstrated to support achieving the desired features when applied in RF UWB transmitters, introducing extremely wide operation and instantaneous bandwidth, tunable filtering, tunable photonics-based microwave mixing with very high port-to-port isolation, and intrinsic immunity to electromagnetic interferences. Moreover, the recent advances in photonics integration also allow to obtain very compact devices. In this article, to the best of our knowledge, the first example of a complete tunable software-defined RF transmitter with low footprint (i.e. on photonic chip) is presented exceeding the state-of-the-art for the extremely large tunability range of 0.5-50 GHz without any parallelization of narrower-band components and with fast tuning (< 200 s). This first implementation represents a breakthrough in microwave photonics

Transmetteurs photoniques sur silicium pour les transmissions optiques à grande capacité

Les applications exigeant des très nombreuses données (médias sociaux, diffusion vidéo en continu, mégadonnées, etc.) se développent à un rythme rapide, ce qui nécessite de plus en plus de liaisons optiques ultra-rapides. Ceci implique le développment des transmetteurs optiques intégrés et à bas coût et plus particulirement en photonique sur silicium en raison de ses avantages par rapport aux autres technologies (LiNbO3 et InP), tel que la compatibilité avec le procédé de fabrication CMOS. Les modulateurs optoélectronique sont un élément essentiel dans la communication op-tique. Beaucoup de travaux de recherche sont consacrées au développement de dispositifs optiques haut débit efficaces. Cependant, la conception de modulateurs en photonique sur sili-cium (SiP) haut débit est diffcile, principalement en raison de l'absence d'effet électro-optique intrinsèque dans le silicium. De nouvelles approches et de architectures plus performances doivent être développées afin de satisfaire aux critères réliés au système d'une liaison optique aux paramètres de conception au niveau du dispositif integré. En outre, la co-conception de circuits integrés photoniques sur silicium et CMOS est cruciale pour atteindre tout le potentiel de la technologie de photonique sur silicium. Ainsi cette thèse aborde les défits susmentionnés. Dans notre première contribution, nous préesentons pour la première fois un émetteur phononique sur silicium PAM-4 sans utiliser un convertisseur numérique analog (DAC)qui comprend un modulateur Mach Zehnder à électrodes segmentées SiP (LES-MZM) implémenté dans un procédé photonique sur silicium générique avec jonction PN latérale et son conducteur CMOS intégré. Des débits allant jusqu'à 38 Gb/s/chnnel sont obtenus sans utili-ser un convertisseur numérique-analogique externe. Nous présentons également une nouvelle procédure de génération de délai dans le excitateur de MOS complémentaire. Un effet, un délai robuste aussi petit que 7 ps est généré entre les canaux de conduite. Dans notre deuxième contribution, nous présentons pour la première fois un nouveau fac-teur de mérite (FDM) pour les modulateurs SiP qui inclut non seulement la perte optique et l'efficacité (comme les FDMs précédents), mais aussi la bande passante électro-optique du modulateur SiP (BWEO). Ce nouveau FDM peut faire correspondre les paramètres de conception physique du modulateur SiP à ses critères de performance au niveau du système, facilitant à la fois la conception du dispositif optique et l'optimisation du système. Pour la première fois nous définissons et utilisons la pénalité de puissance du modulateur (MPP) induite par le modulateur SiP pour étudier la dégradation des performances au niveau du système induite par le modulateur SiP dans une communication à base de modulation d'amplitude d'impulsion optique. Nous avons développé l'équation pour MPP qui inclut les facteurs de limitation du modulateur (perte optique, taux d'extinction limité et limitation de la bande passante électro-optique). Enfin, dans notre troisième contribution, une nouvelle méthodologie de conception pour les modulateurs en SiP intégré à haute débit est présentée. La nouvelle approche est basée sur la minimisation de la MPP SiP en optimisant l'architecture du modulateur et le point de fonctionnement. Pour ce processus, une conception en longueur unitaire du modulateur Mach Zehnder (MZM) peut être optimisée en suivant les spécifications du procédé de fabrication et les règles de conception. Cependant, la longueur et la tension de biais du d'éphaseur doivent être optimisées ensemble (par exemple selon vitesse de transmission et format de modulation). Pour vérifier l'approche d'optimisation proposée expérimentale mont, a conçu un modulateur photonique sur silicium en phase / quadrature de phase (IQ) ciblant le format de modulation 16-QAM à 60 Gigabaud. Les résultats expérimentaux prouvent la fiabilité de la méthodologie proposée. D'ailleurs, nous avons augmenté la vitesse de transmission jusqu'à 70 Gigabaud pour tester la limite de débit au système. Une transmission de données dos à dos avec des débits binaires de plus de 233 Gigabit/s/channel est observée. Cette méthodologie de conception ouvre ainsi la voie à la conception de la prochaine génération d'émetteurs intégrés à double polarisation 400+ Gigabit/s/channel.Data-hungry applications (social media, video streaming, big data, etc.) are expanding at a fast pace, growing demand for ultra-fast optical links. This driving force reveals need for low-cost, integrated optical transmitters and pushes research in silicon photonics because of its advantages over other platforms (i.e. LiNbO3 and InP), such as compatibility with CMOS fabrication processes, the ability of on-chip polarization manipulation, and cost effciency. Electro-optic modulators are an essential component of optical communication links and immense research is dedicated to developing effcient high-bitrate devices. However, the design of high-capacity Silicon Photonics (SiP) transmitters is challenging, mainly due to lack of inherent electro-optic effect in silicon. New design methodologies and performance merits have to be developed in order to map the system-level criteria of an optical link to the design parameters in device-level. In addition, co-design of silicon photonics and CMOS integrated circuits is crucial to reveal the full potential of silicon photonics. This thesis addresses the aforementioned challenges. In our frst contribution, for the frst time we present a DAC-less PAM-4 silicon photonic transmitter that includes a SiP lumped-element segmented-electrode Mach Zehnder modula-tor (LES-MZM) implemented in a generic silicon photonic process with lateral p-n junction and its co-designed CMOS driver. Using post processing, bitrates up to 38 Gb/s/channel are achieved without using an external digital to analog converter. We also presents a novel delay generation procedure in the CMOS driver. A robust delay as small as 7 ps is generated between the driving channels. In our second contribution, for the frst time we present a new figure of merit (FOM) for SiP modulators that includes not only the optical loss and effciency (like the prior FOMs), but also the SiP modulator electro-optic bandwidth ( BWEO). This new FOM can map SiP modulator physical design parameters to its system-level performance criteria, facilitating both device design and system optimization. For the frst time we define and employ the modulator power penalty (MPP) induced by the SiP modulator to study the system level performance degradation induced by SiP modulator in an optical pulse amplitude modulation link. We develope a closed-form equation for MPP that includes the SiP modulator limiting factors (optical loss, limited extinction ratio and electro-optic bandwidth limitation). Finally in our third contribution, we present a novel design methodology for integrated high capacity SiP modulators. The new approach is based on minimizing the power penalty of a SiP modulator (MPP) by optimizing modulator design and bias point. For the given process, a unit-length design of Mach Zehnder modulator (MZM) can be optimized following the process specifications and design rules. However, the length and the bias voltage of the phase shifter must be optimized together in a system context (e.g., baud rate and modulation format). Moreover, to verify the proposed optimization approach in experiment, we design an in-phase/quadrature-phase (IQ) silicon photonic modulator targeting 16-QAM modulation format at 60 Gbaud. Experimental results proves the reliability of our proposed methodology. We further push the baud rate up to 70 Gbaud to examine the capacity boundary of the device. Back to back data transmission with bitrates more than 233 Gb/s/channel are captured. This design methodology paves the way for designing the next generation of integrated dual- polarization 400+ Gb/s/channel transmitters

Dynamic Optical Networks for Data Centres and Media Production

This thesis explores all-optical networks for data centres, with a particular focus on network designs for live media production. A design for an all-optical data centre network is presented, with experimental verification of the feasibility of the network data plane. The design uses fast tunable (< 200 ns) lasers and coherent receivers across a passive optical star coupler core, forming a network capable of reaching over 1000 nodes. Experimental transmission of 25 Gb/s data across the network core, with combined wavelength switching and time division multiplexing (WS-TDM), is demonstrated. Enhancements to laser tuning time via current pre-emphasis are discussed, including experimental demonstration of fast wavelength switching (< 35 ns) of a single laser between all combinations of 96 wavelengths spaced at 50 GHz over a range wider than the optical C-band. Methods of increasing the overall network throughput by using a higher complexity modulation format are also described, along with designs for line codes to enable pulse amplitude modulation across the WS-TDM network core. The construction of an optical star coupler network core is investigated, by evaluating methods of constructing large star couplers from smaller optical coupler components. By using optical circuit switches to rearrange star coupler connectivity, the network can be partitioned, creating independent reserves of bandwidth and resulting in increased overall network throughput. Several topologies for constructing a star from optical couplers are compared, and algorithms for optimum construction methods are presented. All of the designs target strict criteria for the flexible and dynamic creation of multicast groups, which will enable future live media production workflows in data centres. The data throughput performance of the network designs is simulated under synthetic and practical media production traffic scenarios, showing improved throughput when reconfigurable star couplers are used compared to a single large star. An energy consumption evaluation shows reduced network power consumption compared to incumbent and other proposed data centre network technologies

Laser Frequency Combs for Coherent Optical Communications

Laser frequency combs with repetition rates on the order of 10 GHz and higher can he used as multi-carrier sources in wavelength-division multiplexing (WDM). They allow replacing tens of tunable continuous-wave lasers by a single laser source. In addition, the comb\u27s line spacing stability and broadband phase coherence enable signal processing beyond what is possible with an array of independent lasers. Modern WDM systems operate with advanced modulation formats and coherent receivers. This introduces stringent requirements in terms of signal-to-noise ratio, power per line, and optical linewidth which can be challenging to attain for frequency comb sources. Here, we set quantitative benchmarks for these characteristics and discuss tradeoffs in terms of transmission reach and achievable data rates. We also highlight recent achievements for comb-based superchannels, including &gt;10 Tb/s transmission with extremely high spectral efficiency, and the possibility to significantly simplify the coherent receiver by realizing joint digital signal processing. We finally discuss advances with microresonator frequency combs and compare their performance in terms of flatness and conversion efficiency against state-of-the-art electro-optic frequency comb generators. This contribution provides guidelines for developing frequency comb sources in coherent fiber-optic communication systems

Chip-Based Measurement-Device-Independent Quantum Key Distribution

Modern communication strives towards provably secure systems which can be widely deployed. Quantum key distribution provides a methodology to verify the integrity and security of a key exchange based on physical laws. However, physical systems often fall short of theoretical models, meaning they can be compromised through uncharacterized side-channels. The complexity of detection means that the measurement system is a vulnerable target for an adversary. Here, we present secure key exchange up to 200 km while removing all side-channels from the measurement system. We use mass-manufacturable, monolithically integrated transmitters that represent an accessible, quantum-ready communication platform. This work demonstrates a network topology that allows secure equipment sharing which is accessible with a cost-effective transmitter, significantly reducing the barrier for widespread uptake of quantum-secured communication

Scalable multi-chip quantum architectures enabled by cryogenic hybrid wireless/quantum-coherent network-in-package

The grand challenge of scaling up quantum computers requires a full-stack architectural standpoint. In this position paper, we will present the vision of a new generation of scalable quantum computing architectures featuring distributed quantum cores (Qcores) interconnected via quantum-coherent qubit state transfer links and orchestrated via an integrated wireless interconnect.Comment: 5 pages, 2 figures, accepted for presentation at the IEEE International Symposium on Circuits and Systems (ISCAS) 202