Photonic integrated circuit based FMCW coherent LiDAR

We present the demonstration of an integrated Frequency Modulated Continuous Wave LiDAR on a silicon platform. The waveform calibration, the scanning system and the balanced detectors are implemented on chip. Detection and ranging of a moving hard target at up to 60 m with less than 5 mW of output power is demonstrated here

Boucles à verrouillage de phase optique pour la génération de signaux hyperfréquences en bande 5G

One of the key technological issues in the development of future wireless communications network like 5G is the settlement of the new frequencies higher than the classical sub-6 GHz bands, and called millimeter waves (above 30 GHz). Indeed, at these frequencies electronic sources are very expensive, have a high-power consumption and occupy a lot of space, which make them unsuitable for embedded and remote applications. As a replacement optical coherent technology is in first position due to its high compatibility with the already fibered network while requiring very few elements at remote sites, like antennas for instance. Furthermore, the maturity level reached by photonic integrated circuits is now at a decisive moment when they can be used massively within coherent transmission components. This being combined with a downscale of antenna size, due to lower wavelength in millimeter wave, allows new architectures to introduce beamforming and spatial division multiplexing to increase network fronthaul capacity. Among all optically assisted millimeter wave generation methods the one we deal with in this work is named optical phase lock loop, which compatibility with standardized photonic integrated circuits is also investigated. The working principle relies on an electronic feedback loop making optical phase variations of two independent lasers correlated, and their resulting beat note being then artificially coherent. Thus, the latter is very easy to use in order operate optically assisted frequency up- and down-conversion of a millimeter wave signal. This method benefits from strong assets like its high available optical power and its flexibility toward complex photonics architectures which makes it very suitable to supply photonic integrated circuits dedicated to signal processing, as beamforming networks for instance. In this work we developed an optical phase lock loop based on commercially available fibered components in order to demonstrate the viability of using semiconductor lasers for coherent applications. This loop has then been implemented in several transmission schemes in the K-band (20-30 GHz) for future 5G experiments, all within the blueSPACE European project. This has led us to investigate the effect of the loop phase noise on QAM modulation formats and OFDM method, both being standards for 5G and beyond. In parallel we designed an optical phase lock loop photonic integrated circuit, which fabrication has been subcontracted to a commercial indium phosphide foundry, in order to evaluate the maturity of the process towards high complexity devices.L’un des principaux verrous technologiques inhérents au développement des nouvelles technologies de communications sans-fil, comme la 5G, est la transition des fréquences radios classiques, inférieures à 6 GHz, vers le domaine des ondes millimétriques, au-delà de 30 GHz. En effet, les sources électroniques permettant de générer de telles ondes ne sont pas compatibles avec les applications visées, notamment le déploiement au sein d’unités déportées, car trop volumineuses, coûteuses et gourmandes en énergie. Pour les remplacer, les technologies optiques cohérentes font office de favorites car elles permettent de bénéficier des infrastructures déjà déployées en fibre optique tout en minimisant les éléments nécessaires au niveau des antennes. Par ailleurs, la maturité des circuits photoniques intégrés arrive à un point décisif aujourd’hui ce qui permet d’envisager leur usage massif dans les futurs dispositifs de transmissions cohérentes. L’association de ces technologies avec la réduction de la taille des antennes dans le domaine millimétrique débloque également l’accès à des solutions comme la formation de faisceaux et le multiplexage spatial, dont les utilisations dans ce contexte étaient jusqu’ici limitées. Parmi les techniques de génération d’ondes millimétriques par voie optique nous avons décidé d’étudier dans ces travaux la boucle à verrouillage de phase optique, ainsi que sa compatibilité avec les technologies de fonderies commerciales pour la réalisation de circuits intégrés. Le principe repose sur l’asservissement, à l’aide de correcteurs électroniques, des variations de phase de deux lasers dans le but de les rendre artificiellement cohérents. Le battement de ces deux lasers peut alors être facilement utilisé pour effectuer une montée en fréquence de la bande de base vers le domaine millimétrique. Les avantages de cette technique reposent sur une forte puissance optique disponible alliée à une grande flexibilité d’architecture, ce qui convient particulièrement bien à une utilisation au sein de circuits photoniques de traitement de plus en plus complexes. Dans ces travaux nous avons d’abord développé une boucle à base de composants télécoms fibrés commerciaux afin de montrer la viabilité de l’utilisation des lasers à semi-conducteurs au sein de ce genre de dispositif. Cette boucle a été ensuite implémentée dans diverses expériences de transmissions en bande K (20-30 GHz) au sein du démonstrateur du projet européen blueSPACE sur la 5G, ce qui nous a permis d’étudier la robustesse de la boucle en termes de bruit de phase relativement aux formats de modulations QAM et à la méthode OFDM, standards pour la future 5G. En parallèle nous avons conçu un circuit photonique de boucle à verrouillage de phase dont nous avons ensuite sous-traité la fabrication à une fonderie commerciale afin d’évaluer la maturité du procédé de fabrication pour la réalisation de ce genre de composant

Optical phase-locked loops for microwave generation in 5G frequency bands

L’un des principaux verrous technologiques inhérents au développement des nouvelles technologies de communications sans-fil, comme la 5G, est la transition des fréquences radios classiques, inférieures à 6 GHz, vers le domaine des ondes millimétriques, au-delà de 30 GHz. En effet, les sources électroniques permettant de générer de telles ondes ne sont pas compatibles avec les applications visées, notamment le déploiement au sein d’unités déportées, car trop volumineuses, coûteuses et gourmandes en énergie. Pour les remplacer, les technologies optiques cohérentes font office de favorites car elles permettent de bénéficier des infrastructures déjà déployées en fibre optique tout en minimisant les éléments nécessaires au niveau des antennes. Par ailleurs, la maturité des circuits photoniques intégrés arrive à un point décisif aujourd’hui ce qui permet d’envisager leur usage massif dans les futurs dispositifs de transmissions cohérentes. L’association de ces technologies avec la réduction de la taille des antennes dans le domaine millimétrique débloque également l’accès à des solutions comme la formation de faisceaux et le multiplexage spatial, dont les utilisations dans ce contexte étaient jusqu’ici limitées. Parmi les techniques de génération d’ondes millimétriques par voie optique nous avons décidé d’étudier dans ces travaux la boucle à verrouillage de phase optique, ainsi que sa compatibilité avec les technologies de fonderies commerciales pour la réalisation de circuits intégrés. Le principe repose sur l’asservissement, à l’aide de correcteurs électroniques, des variations de phase de deux lasers dans le but de les rendre artificiellement cohérents. Le battement de ces deux lasers peut alors être facilement utilisé pour effectuer une montée en fréquence de la bande de base vers le domaine millimétrique. Les avantages de cette technique reposent sur une forte puissance optique disponible alliée à une grande flexibilité d’architecture, ce qui convient particulièrement bien à une utilisation au sein de circuits photoniques de traitement de plus en plus complexes. Dans ces travaux nous avons d’abord développé une boucle à base de composants télécoms fibrés commerciaux afin de montrer la viabilité de l’utilisation des lasers à semi-conducteurs au sein de ce genre de dispositif. Cette boucle a été ensuite implémentée dans diverses expériences de transmissions en bande K (20-30 GHz) au sein du démonstrateur du projet européen blueSPACE sur la 5G, ce qui nous a permis d’étudier la robustesse de la boucle en termes de bruit de phase relativement aux formats de modulations QAM et à la méthode OFDM, standards pour la future 5G. En parallèle nous avons conçu un circuit photonique de boucle à verrouillage de phase dont nous avons ensuite sous-traité la fabrication à une fonderie commerciale afin d’évaluer la maturité du procédé de fabrication pour la réalisation de ce genre de composant.One of the key technological issues in the development of future wireless communications network like 5G is the settlement of the new frequencies higher than the classical sub-6 GHz bands, and called millimeter waves (above 30 GHz). Indeed, at these frequencies electronic sources are very expensive, have a high-power consumption and occupy a lot of space, which make them unsuitable for embedded and remote applications. As a replacement optical coherent technology is in first position due to its high compatibility with the already fibered network while requiring very few elements at remote sites, like antennas for instance. Furthermore, the maturity level reached by photonic integrated circuits is now at a decisive moment when they can be used massively within coherent transmission components. This being combined with a downscale of antenna size, due to lower wavelength in millimeter wave, allows new architectures to introduce beamforming and spatial division multiplexing to increase network fronthaul capacity. Among all optically assisted millimeter wave generation methods the one we deal with in this work is named optical phase lock loop, which compatibility with standardized photonic integrated circuits is also investigated. The working principle relies on an electronic feedback loop making optical phase variations of two independent lasers correlated, and their resulting beat note being then artificially coherent. Thus, the latter is very easy to use in order operate optically assisted frequency up- and down-conversion of a millimeter wave signal. This method benefits from strong assets like its high available optical power and its flexibility toward complex photonics architectures which makes it very suitable to supply photonic integrated circuits dedicated to signal processing, as beamforming networks for instance. In this work we developed an optical phase lock loop based on commercially available fibered components in order to demonstrate the viability of using semiconductor lasers for coherent applications. This loop has then been implemented in several transmission schemes in the K-band (20-30 GHz) for future 5G experiments, all within the blueSPACE European project. This has led us to investigate the effect of the loop phase noise on QAM modulation formats and OFDM method, both being standards for 5G and beyond. In parallel we designed an optical phase lock loop photonic integrated circuit, which fabrication has been subcontracted to a commercial indium phosphide foundry, in order to evaluate the maturity of the process towards high complexity devices

Experimental ARoF System Based on OPLL Mm-Wave Generation for Beyond 5G

We experimentally analyze the ARoF based on OPLL mm-Wave generation performance for 5G fronthaul. Remarkable performance improvements are achieved for all 5G NR numerologies and different OPLL configurations despite their inherently high phase noise level

Optical phase-locked loop phase noise in 5G mm-wave OFDM ARoF systems

The use of millimeter-wave (mm-wave) frequencies is required in order to support the increasing number of connected devices expected from the fifth generation (5G) of mobile communications. Subsequently, the generation of radio-frequency (RF) carriers ranging from 10 GHz to 300 GHz and their transport through optical distribution network (ODN) is a key element of the future 5G fronthaul. Optically assisted RF carrier generation is one of the most promising solutions to tackle this issue, allowing a wide use of analog radio-over-fiber (ARoF) architectures. However the main limitation of these optical methods is related to the finite coherence of lasers sources, which can dramatically degrade data transmission in analog formats. To mitigate its impact, the use of orthogonal frequency-division multiplexing (OFDM) as the 5G standard allows employing efficient phase noise compensation algorithms. Therefore, in this study, we present an experimental demonstration of a mm-wave generation technique based on an optical phase-locked loop (OPLL) that fulfills the frequency specifications for 5G. Then, an algorithm is introduced that improves data recovery at reception and reduces the impact of a possible high phase noise carrier. Finally, a back-to-back data transmission experiment is performed, demonstrating the efficiency of the algorithm to reach the 5G requirements. These results emphasize the use of OPLLs as a viable solution to generate mm-wave carriers for 5G and beyond

Real-time high-bandwidth mm-wave 5G NR signal transmission with analog radio-over-fiber fronthaul over multi-core fiber

This article presents an experimental demonstration of a high-capacity millimeter-wave 5G NR signal transmission with analog radio-over-fiber (ARoF) fronthaul over multi-core fiber and full real-time processing. The demonstration validates the core of the blueSPACE fronthaul architecture which combines ARoF fronthaul with space division multiplexing in the optical distribution network to alleviate the fronthaul capacity bottleneck and maintain a centralized radio access network with fully centralized signal processing. The introduction of optical beamforming in the blueSPACE architecture brings true multi-beam transmission and enables full spatial control over the RF signal. The proposed ARoF architecture features a transmitter that generates the ARoF signal and an optical signal carrying a reference local oscillator employed for downconversion at the remote unit from a single RF reference at the central office. A space division multiplexing based radio access network with multi-core fibre allows parallel transport of the uplink ARoF signal and reference local oscillator at the same wavelength over separate cores. A complete description of the real-time signal processing and experimental setup is provided and system performance is evaluated. Transmission of an 800 MHz wide extended 5G NR fronthaul signal over a 7-core fibre is shown with full real-time signal processing, achieving 1.4 Gbit/s with a bit error rate < 3.8 × 10 - 3 and thus below the limit for hard-decision forward error correction with 7% overhead

Real-time demonstration of ARoF fronthaul for high-bandwidth mm-Wave 5G NR signal transmission over multi-core fiber

This paper presents an experimental demonstration of analog radio-over-fiber (ARoF) fronthaul for high-bandwidth, high-capacity millimeter wave (mm-wave) extended fifth generation mobile network (5G) new radio (NR) signals over an optical distribution network with optical space division multiplexing (SDM). ARoF is shown to alleviate fronthaul capacity bottlenecks, transporting an 800 MHz wide extended 5G NR signal and allowing to maintain full centralization in a centralized radio access network (C-RAN). The proposed ARoF fronthaul architecture features a transmitter that generates the ARoF signal and an optical signal carrying a reference local oscillator (LO) employed for downconversion at the remote unit (RU) from a single radio frequency (RF) reference at the central office (CO). An SDM based RAN with 7-core multi-core fiber (MCF) allows parallel transport of the uplink ARoF signal and reference LO at the same wavelength over separate cores. Transmission of an 800 MHz wide extended 5G NR fronthaul signal over 7-core MCF is shown with full real-time processing, achieving 1.4 Gbit/s with BER<3.8 × 10-3 and thus below the limit for hard-decision forward error correction (FEC) with 7 % overhead. Downconversion at the RU is performed electrically with the remote-fed LO provided by the CO

Towards a Scaleable 5G Fronthaul: Analog Radio-over-Fiber and Space Division Multiplexing

The introduction of millimeter wave (mm-wave) frequency bands for cellular communications with significantly larger bandwidths compared to their sub-6GHz counterparts, the resulting densification of network deployments and the introduction of antenna arrays with beamforming result in major increases in fronthaul capacity required for 5G networks. As a result, a radical re-design of the radio access network is required since traditional fronthaul technologies are not scaleable. In this article the use of analog radio over fiber (ARoF) is proposed and demonstrated as a viable alternative which, combined with space division multiplexing in the optical distribution network as well as photonic integration of the required transceivers, shows a path to a scaleable fronthaul solution for 5G. The trade-off between digitized and analog fronthaul is discussed and the ARoF architecture proposed by blueSPACE is introduced. Two options for the generation of ARoF two-tone signals for mm-wave generation via optical heterodyning are discussed in detail, including designs for the implementation in photonic integrated circuits as well as measurements of their phase noise performance. The proposed photonic integrated circuit designs include the use of both InP and SiN platforms for ARoF signal generation and optical beamforming respectively, proposing a joint design that allows for true multi-beam transmission from a single antenna array. Phase noise measurements based on laboratory implementations of ARoF generation based on a Mach-Zehnder modulator with suppressed carrier and with an optical phase-locked loop are presented and the suitability of these transmitters is evaluated though phase noise simulations. Finally, the viability of the proposed ARoF fronthaul architecture for the transport of high-bandwidth mm-wave 5G signals is proven with the successful implementation of a real-time transmission link based on an ARoF baseband unit with full real-time processing of extended 5G new radio signals with 800MHz bandwidth, achieving transmission over 10km of 7-core single-mode multi-core fiber and 9m mm-wave wireless at 25.5GHz with bit error rates below the limit for a 7% overhead hard decision forward error correction

Towards a Scaleable 5G Fronthaul: Analog Radio-over-Fiber and Space Division Multiplexing

The introduction of millimeter wave (mm-wave) frequency bands for cellular communications with significantly larger bandwidths compared to their sub-6GHz counterparts, the resulting densification of network deployments and the introduction of antenna arrays with beamforming result in major increases in fronthaul capacity required for 5G networks. As a result, a radical re-design of the radio access network is required since traditional fronthaul technologies are not scaleable. In this article the use of analog radio over fiber (ARoF) is proposed and demonstrated as a viable alternative which, combined with space division multiplexing in the optical distribution network as well as photonic integration of the required transceivers, shows a path to a scaleable fronthaul solution for 5G. The trade-off between digitized and analog fronthaul is discussed and the ARoF architecture proposed by blueSPACE is introduced. Two options for the generation of ARoF two-tone signals for mm-wave generation via optical heterodyning are discussed in detail, including designs for the implementation in photonic integrated circuits as well as measurements of their phase noise performance. The proposed photonic integrated circuit designs include the use of both InP and SiN platforms for ARoF signal generation and optical beamforming respectively, proposing a joint design that allows for true multi-beam transmission from a single antenna array. Phase noise measurements based on laboratory implementations of ARoF generation based on a Mach-Zehnder modulator with suppressed carrier and with an optical phase-locked loop are presented and the suitability of these transmitters is evaluated though phase noise simulations. Finally, the viability of the proposed ARoF fronthaul architecture for the transport of high-bandwidth mm-wave 5G signals is proven with the successful implementation of a real-time transmission link based on an ARoF baseband unit with full real-time processing of extended 5G new radio signals with 800MHz bandwidth, achieving transmission over 10km of 7-core single-mode multi-core fiber and 9m mm-wave wireless at 25.5GHz with bit error rates below the limit for a 7% overhead hard decision forward error correction