Recent advances in radiation-hardened fiber-based technologies for space applications

International audience; In this topical review, the recent progress on radiation-hardened fiber-based technologies is detailed, focusing on examples for space applications. In the first part of the review, we introduce the operational principles of the various fiber-based technologies considered for use in radiation environments: passive optical fibers for data links, diagnostics, active optical fibers for amplifiers and laser sources as well as the different classes of point and distributed fiber sensors: gyroscopes, Bragg gratings, Rayleigh, Raman or Brillouin-based distributed sensors. Second, we describe the state of the art regarding our knowledge of radiation effects on the performance of these devices, from the microscopic effects observed in the amorphous silica glass used to design fiber cores and cladding, to the macroscopic response of fiber-based devices and systems. Third, we present the recent advances regarding the hardening (improvement of the radiation tolerance) of these technologies acting on the material, device or system levels. From the review, the potential of fiber-based technologies for operation in radiation environments is demonstrated and the future challenges to be overcome in the coming years are presented

Les fibres optiques dopées aux terres rares et amplificateurs optiques pour applications spatiales

Rare earth doped fibers (REDFs) are a key component in optical laser sources and amplifiers (REDFAs). Their high performances render them very attractive for space applications as the active part of gyroscopes, high data transfer links and LIDARs. However, the high sensitivity of these active fibers to space radiations limits the REDFA integration in actual and future missions. To overcome these issues various studies were carried out and some mitigation techniques were identified such as the Cerium co-doping or the hydrogen loading of the REDFs. All these solutions occur at the component level and are classified as a hardening by component strategy allowing the manufacturing of radiation hardened REDFAs with adapted performances for low doses space mission. However, with the new space research programs, more challenging space missions are targeted with higher radiations doses requiring even more tolerant REDFs and REDFAs. To this aim, an optimization of the REDFA at the system level is investigated in this PhD thesis exploiting an approach coupling simulations and experiments offering the opportunity to benefit from the outputs of this hardening by system strategy in addition to other state-of-the-art approaches. After presenting the context, objectives of this work, the basic mechanisms about amplification and radiation effects as well as the architectures of REDFAs are described in chapters I and II. After that, we update a state of art REDFAs simulation code described in Chapter III, to consider not only the REDFA optical performances but also their evolutions when exposed to radiations. Several experiments on dedicated home-made REDFA have been performed using accelerated irradiation tests (Chapter IV) and the comparison between these data and those obtained through the new code validated the simulation tools. Thereafter, we exploit the validated code to highlight how the optimization of the REDFA architecture can participate to the mitigation of the radiation effects on the amplifier performances (Chapter V). Finally, in chapter VI the implementation in the code of several other effects, such as thermal effects, input signal multiplexing was investigated both from experimental and calculation point of viewsLes fibres dopées aux terres rares (REDFs) représentent un composant clef dans la fabrication de sources laser et d’amplificateurs optiques (REDFAs). Leurs hautes performances rendent cette technologie particulièrement attractive pour les applications spatiales en tant que partie active des gyroscopes à fibres optiques, pour le transfert de données et les applications LIDARS. Cependant, la grande sensibilité de ces fibres actives limite l’intégration des REDFAs au sein des missions spatiales. De nombreuses études ont été menées pour dépasser ces limitations et différentes techniques de mitigation ont été identifiées telles que le co-dopage au Cérium ou le chargement en hydrogène de ces fibres optiques. Toutes ces solutions interviennent au niveau du composant sensible et sont classées parmi les stratégies de durcissement par composant permettant la fabrication de fibres dopées aux terres rares résistantes aux radiations adaptées aux besoins des missions spatiales actuelles associées à de faibles doses d’irradiation. Cependant, l’avènement de nouveaux programmes, de nouvelles missions invitent à considérer des doses d’irradiation plus importantes, nécessitant des REDFs et des RDFAs encore plus tolérants aux radiations. A cette fin, une optimisation de l’amplificateur optique au niveau système est étudiée dans le cadre de ce doctorat en exploitant une approche couplant simulation et expériences dont les avancées pourront venir en appui des techniques de durcissement plus conventionnelles. Après la présentation du contexte, des objectifs de ce travail (Chapitre I), les mécanismes fondamentaux de l’amplification et des effets des radiations sont brièvement décrits dans le Chapitre II. Les outils de simulation basés sur l’enrichissement d’un code à l’état de l’art et ses nouvelles fonctionnalités, décrites au Chapitre III, permettent non seulement l’évaluation des performances optiques du REDFA mais aussi de prédire leurs évolutions sous irradiation. De nombreuses études expérimentales ont été réalisées sur différents REDFAs développés durant la thèse et présentés dans le chapitre IV, leurs résultats comparés à ceux issus de la simulation afin de valider nos outils de simulation. Une fois validé, le code a été utilisé pour montrer comment l’optimisation de l’architecture du REDFA permet de mitiger les effets des radiations sur ses performances (Chapitre V). Finalement, le Chapitre VI présente l’étude de l’implémentation dans le code de nouveaux effets, tels que les effets thermiques, le multiplexage du signal d’entrée à travers un couplage théorie/expérienc

Fibres optiques dopées aux terres rares et amplificateurs optiques pour applications spatiales

International audienceDes outils de simulation multi-physiques des nous permettent de prédire les performances d’un amplificateur optique à base de fibre active Er ou Er/Yb en terme de gain et de bruit. Les travaux présentés visent à implémenter un module additionnel en vue de prédire leur comportement sous irradiation. Dans sa version publiée, les pertes induites par l’irradiation sont les seuls paramètres pris en compte dans ce module. Dans cet article, nous étudions l’influence d’une altération sous irradiation des autres paramètres spectroscopiques sur le gain et le bruit de l’amplification afin d’identifier les optimisations les plus pertinentes pour nos codes de calcu

Laser Powder Bed Fusion thermal monitoring using optical fiber sensors: in situ measurements and modelling

International audienceWe performed temperature measurements in a part manufactured by Laser Powder Bed Fusion using optical fiber sensors. A simplified model of the process was developed, and the experimental measurements are compared to simulated temperature values

Impact on mechanical properties following the insertion of an optical sensor during additive manufacturing

International audienceOver the past decade, additive manufacturing has made a tremendous progress. More ever, additive manufacturing get a great interest to the development of mechanical parts with complex geometries and compositions. This design freedom allows the additive manufacturing process to be used to integrate optical sensors during the printing process, making it possible to produce instrumented components for SHM (structural health monitoring). The latter required a particular process with adapted printing strategy and an interruption of the procedure in order to place the sensor. The impact of these modifications on the parts mechanical properties needs to be investigated in order to determine the influence of the sensor insertion on the mechanical parts behaviors. In this work, we perform several experiments on different 3D Printed parts with and without sensor insertion. The focus is to identify the best procedure that minimize the impact of the sensor insertion on the mechanical properties

Online optical refractive index measurement in research reactor core

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Selective laser melting In SituIn\ Situ temperature monitoring using femtosecond point-by-point Fiber Bragg Gratings

International audienceDynamic temperature monitoring along a stainless steel specimen additively manufactured by selective laser melting was performed using point-by-point written femtosecond Fiber Bragg Gratings packaged in a metallic capillary

Impact on mechanical properties following the insertion of an optical sensor during additive manufacturing

International audienceOver the past decade, additive manufacturing has made a tremendous progress. More ever, additive manufacturing get a great interest to the development of mechanical parts with complex geometries and compositions. This design freedom allows the additive manufacturing process to be used to integrate optical sensors during the printing process, making it possible to produce instrumented components for SHM (structural health monitoring). The latter required a particular process with adapted printing strategy and an interruption of the procedure in order to place the sensor. The impact of these modifications on the parts mechanical properties needs to be investigated in order to determine the influence of the sensor insertion on the mechanical parts behaviors. In this work, we perform several experiments on different 3D Printed parts with and without sensor insertion. The focus is to identify the best procedure that minimize the impact of the sensor insertion on the mechanical properties

Evaluation of the radiation effect on the rare-earth spectroscopic parameters for the optical amplifier simulation in space environment

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Optimized radiation-hardened erbium doped fiber amplifiers for long space missions

International audienceIn this work, we developed and exploited simulation tools to optimize the performances of rare earth doped fiber amplifiers (REDFAs) for space missions. To describe these systems, a state-of-the-art model based on the rate equations and the particle swarm optimization technique is developed in which we also consider the main radiation effect on REDFA: the radiation induced attenuation (RIA). After the validation of this tool set by confrontation between theoretical and experimental results, we investigate how the deleterious radiation effects on the amplifier performance can be mitigated following adequate strategies to conceive the REDFA architecture. The tool set was validated by comparing the calculated Erbium-doped fiber amplifier (EDFA) gain degradation under X-rays at ∼300 krad(SiO2) with the corresponding experimental results. Two versions of the same fibers were used in this work, a standard optical fiber and a radiation hardened fiber, obtained by loading the previous fiber with hydrogen gas. Based on these fibers, standard and radiation hardened EDFAs were manufactured and tested in different operating configurations, and the obtained data were compared with simulation data done considering the same EDFA structure and fiber properties. This comparison reveals a good agreement between simulated gain and experimental data (<10% as the maximum error for the highest doses). Compared to our previous results obtained on Er/Yb-amplifiers, these results reveal the importance of the photo-bleaching mechanism competing with the RIA that cannot be neglected for the modeling of the radiation-induced gain degradation of EDFAs. This implies to measure in representative conditions the RIA at the pump and signal wavelengths that are used as input parameters for the simulation. The validated numerical codes have then been used to evaluate the potential of some EDFA architecture evolutions in the amplifier performance during the space mission. Optimization of both the fiber length and the EDFA pumping scheme allows us to strongly reduce its radiation vulnerability in terms of gain. The presented approach is a complementary and effective tool for hardening by device techniques and opens new perspectives for the applications of REDFAs and lasers in harsh environments