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In this paper, we present a multiphysics modeling of rare earth-doped cladding-pumped fiber amplifiers to predict the device performance with respect to the constraints associated with space missions. By combining the 3-D nonhomogeneous heat conduction equation with the nonlinear rate equations, the developed numerical algorithm makes possible the calculation of the spatial distribution of the different optical signals and temperature profiles. The temperature dependence of the refractive index, emission, and absorption cross sections, as well as the radiation induced attenuation and the lifetime versus the deposited dose have been considered, too. They lead to the optical signals changing inside the fiber creating a feedback loop that influences the temperature distribution within the fiber. Different operational regimes for a representative fiber design as well as different cooling configurations have been investigated. The obtained numerical results highlight that the thermal field inside the fiber could strongly deteriorate the amplifier performance especially in the space radiation environment.

We investigated the X-ray [40 keV, 700 Gy(SiO2), ~80 mGy/s] radiation effects on the performances (gain) of Er-doped fiber preamplifier (EDFA) and Er/Yb codoped fiber boost amplifier (EYDFA). Various EDFA and EYDFA architectures have been designed to operate either in wavelength division multiplexing (WDM) or dense WDM (DWDM) schemes. We compare the performances of amplifiers based on conventional or radiation-hardened (RH) versions of the active Er-doped or Er/Yb-codoped fibers. Our results show that for all amplifier architectures, the various channels undergo similar gain degradation levels and kinetics, as expected from the measured spectral dependence of the radiation-induced attenuation of the phosphosilicate (ErYb-doped) and aluminosilicate (Er-doped) glass matrixes of these fibers. This degradation remains very limited for the amplifiers based on RH fibers, with a gain decrease of less than 0.3 mdB.Gy−1 for the EDFA (~30 dB initial gain) and less than 0.8 mdB.Gy−1 for the EYDFA (~18 dB initial gain) in the DWDM architecture.

International audience; The evolution of Ytterbium 2F5/2 and Erbium 4I13/2 energy level lifetimes versus doses of various radiation types (40 keV X-rays, 480 MeV protons, 1.2 MeV γ-rays and 6 MeV electrons) were investigated on samples of silica-based Rare-Earth Doped optical Fibers (REDFs). For each studied sample (Er-doped and Er/Yb-doped), a strong dependence of the lifetime value on the irradiation dose (for equivalent doses ranging from 10 Gy(SiO2) to 10 MGy(SiO2)) is observed regardless of the radiation nature. For both fiber types and luminescent ions, complex dose dependences are observed: a limited decrease of the lifetime at the lower doses, whereas a large reduction is reported at doses exceeding 100 kGy(SiO2). The results highlighted the vulnerability of REDF based systems, such as optical amplifiers and sources, for space and nuclear applications. In such harsh environments, Radiation Induced Attenuation (RIA) is also a key issue. The positive effect of Ce co-doping on both the RIA and the lifetimes is reported even at the highest dose of 10 MGy(SiO2). The basic mechanisms involved during the interaction between radiation and fiber material were also investigated through low temperature spectroscopic measurements that revealed the fundamental role of radiation-induced point defects.

The actual challenge for space researchers is to increase the free space telecommunications data speed transfer. One of the most promising solutions is the optical communication systems. This technology can be used for the inter-satellite and/or satellite-ground links, reaching the TB/s speed for data transfer in the case of Dense Wavelengths Division Multiplexing (DWDM) based technologies. However, to achieve such systems, two main issues need to be overcome: the first one is to validate that no unexpected radiation effect appears when the optical amplifier working in the DWDM configuration and the second one is to estimate the degradation of the Erbium/Ytterbium co-doped boost (High Power - HP) amplifier performances during the space mission lifetime. In this last case, the used high powers will result in a complex response of the amplifier due to photobleaching, photodarkening and thermal effects. In this work, we estimate the radiation effects on an Er/Yb co-doped boost amplifier operating in a Dense WDM configuration. Both radiation hardened and a conventional versions of EYDFA have been considered. The obtained results allow estimating the performances of our fibers under exposure in such amplification setup and also to validate its potential for use in an actual space mission. We demonstrate the good radiation resistance of Er/Yb co-doped 12 μm core diameter fibers reaching 20 W of output power for telecommunication applications. This core diameter provides a fewmode optical output signal (with low dispersion) and with enough power to ensure the signal propagation trough the atmosphere. This study is fundamental as several phenomena such as Photo/Thermal bleaching, photo-darkening… are in competition due to the high-power light density in the fiber core and the system radiation response cannot yet be predicted by actual simulation tools.

International audience; The radiation responses of different high-power erbium/ytterbium-codoped fiber amplifiers (HP-EYDFA) have been investigated up to 100 krad (SiO2) dose levels. These devices are able to deliver 20 W of signal output power at 1565 nm by pumping at 915 nm (43 W) radiation tolerant (Er/Yb) or radiation hardened (ErYbCe) active few mode fibers; these performances are needed for free-space communications between low-orbit satellites and ground transceivers. X-ray irradiation results show that, thanks to a positive influence of the photo- and thermal-bleaching phenomena associated with such high-power operating conditions, the gain degradation levels of HP-EYDFA based on radiation hardened fibers remain below 6% after 100 krad at an accelerated dose rate of 3.4 rad/s.

International audience; In this paper, a compendium of InGaAs photodiode irradiation test results is presented. These photodiodes were irradiated either with γ-rays, protons, neutrons, electrons, pions, alpha particles, or carbon ions of various energies. The displacement damage dose formalism was found to be effective in describing the radiation-induced dark current increase of any of the studied InGaAs photodiodes. The exploitation of capacitancebias voltage and current-bias voltage measurements also allows us to deduce a damage factor that can be used to assess the radiation-induced dark current in a great number of radiation environments.

The temperature dependence of the emission and absorption cross sections of Er and Yb ions in rare-earth-doped aluminosilicate optical fibers is experimentally investigated. The obtained results demonstrate that the McCumber theory accurately predicts the temperature-induced changes of the emission cross section spectrum up to 500 °C when the absorption spectra measured at the considered temperature is used for the calculations instead of the one acquired at ambient temperature. Finally, we also demonstrate that the various heating steps up to 500 °C are not affecting the fiber guiding properties and no permanent effect is observed on the emission and absorption cross section spectra measured at room temperature.

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.

A radiation resistant optical fiber used in a broadband source is presented. Both ASE source and Fiber Optical Gyroscope (FOG) commonly used in space missions, suffer from failures and degradation after long term exposure to radiative environment. The aim of this article is to present the results of our investigation on fiber and ASE source architecture in order to design a Radiation Resistant Erbium Doped Fiber that offers long term stability of the gyroscope performances.

In space applications, components may be used at very low temperature. We have studied the ability of a custom designed cryostat developed by CNES to be used for tests under protons with temperature as low as 80 K regarding dosimetry and radiation safety concerns.

In the frame of EUCLID project, the Calibration Unit of the VIS (VISible Imager) instrument must provide an accurate and well characterized light source for in-flight instrument calibration without noise when it is switched off. The Calibration Unit consists of a set of LEDs emitting at various wavelengths in the visible towards an integrating sphere. The sphere’s output provides a uniform illumination over the entire focal plane. Nine references of LEDs from different manufacturers were selected, screened and qualified under cryogenic conditions. Testing this large quantity of samples led to the implementation of automated testing equipment with complete in-situ monitoring of optoelectronic parameters as well as temperature and vacuum values. All the electrical and optical parameters of the LED have been monitored and recorded at ambient and cryogenic temperatures. These results have been compiled in order to show the total deviation of the LED electrical and electro-optical properties in the whole mission and to select the best suitable LED references for the mission. This qualification has demonstrated the robustness of COTS LEDs to operate at low cryogenic temperatures and in the space environment. Then 6 wavelengths were selected and submitted to an EMC sensitivity test at room and cold temperature by counting the number of photons when LEDs drivers are OFF. Characterizations were conducted in the full frequency spectrum in order to implement solutions at system level to suppress the emission of photons when the LED drivers are OFF. LEDs impedance was also characterized at room temperature and cold temperature.

Rare-earth doped optical fibers (REDF, Er or Er/Yb-doped) are a key component in optical laser sources (REDFS) and amplifiers (REDFA). The high performances of these fiber-based systems made them as promising solution part of gyroscopes, telecommunication systems… However, REDFs are very sensitive to space radiations, so their degradation limits their integration in long term space missions. To overcome this issue, several studies were carried out and some innovations at the component level were proposed by our group such as the Cerium co-doping or the hydrogen loading of the REDF. More recently we initiated an original coupled simulation/experiment approach to improve the REDFA performances under irradiation by acting at the system level and not only at the component itself. This procedure optimizes the amplifier properties (gain, noise figure) under irradiation through simulation. The optimization of the system is ensured using a PSO (Particle Swarm optimization) algorithm. Using some experimental inputs, such as the Radiation Induced Attenuation (RIA) measurements and the spectroscopic features of the fiber, we demonstrate its efficiency to reproduce the amplifier degradation when exposed to radiations in various experimental configurations. This was done by comparing the obtained simulation results to those of dedicated experiments performed on various REDFA architectures. Our results reveal a good agreement between simulations and experimental data (with

The radiation tolerance of a 0.18 μm technology CMOS commercial image sensor has been evaluated with Co60 and proton irradiations. The effects of protons on the hot pixels and dynamic bias and duty cycle conditions during gamma irradiations are studied.

Dark current evolution in Charge Coupled Devices (CCD) is experimentally studied with Co-60 and proton irradiations. Linear CCDs are irradiated in various static and dynamic bias conditions. Annealing effects are discussed and on-ground data are compared to in-flight data. Presented results on ionization-induced dark current increase in CCDs have demonstrated the impact of the sensor operational conditions and dose rate, revealing an ELDRS-like effect.

This paper presents the analysis of the CoRoT CCDs dark current degradation measured during more than 2.5 years in orbit. Starting from on-ground irradiation results obtained during the space qualification of the detectors, a model is proposed to calculate the in-orbit pixel dark current distribution (including the hot pixels one). The modeling results are found to be in good agreement with the in-flight data. We therefore use this model to extrapolate the evolution of the dark signal distribution beyond 2.5 years. This is of primary interest in the context of a mission duration extension to 6 years proposed for the CoRoT mission.

This paper presents the CNES analysis of CCD dark current degradation in orbit. For the first time, data coming from several detectors in orbit have been collected and congregated to extract general trends about in-flight detector behaviours. The in-orbit degradation is therefore compared to the on-ground prediction for each detector. This work has been done in collaboration with the CNES detection subsystem office, the CNES image quality office and the CNES components & environment effects office.

We report on a novel method to measure radiation induced non radiative carrier lifetime modifications in laser diodes. This method is based on the conjugation of theoretical gain calculation, experimental gain measurements, and threshold variation measurements. We show that lifetime variations measured that way are in good agreement with those measured using time resolved photoluminescence (TRPL), and that the methodology can be applied to annealed samples, whose carrier lifetime cannot be otherwise measured.

Quantum dash lasers were irradiated for the first time, using 31-MeV protons. These novel structures, which show promising performances for 1.55 mum optical communications exhibit better robustness to radiation than quantum well lasers.

In 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 (

International audience; We investigated the behavior of a new class of erbium-doped fiber amplifier (EDFA) when exposed to 63 MeV protons. The EDFA is designed with a radiation hardened hole-assisted carbon coated (HACC) Er3 + -doped optical fiber. The particular structure of this HACC fiber allows to permanently incorporate an optimal amount of D2 or H2 gases into its core, reducing its radiation sensitivity without degrading the EDFA performances. Irradiations up to a fluence of 7.5 ×1011 p/cm2 confirm the excellent tolerance of this HACC-EDFA component. It exhibits a limited decrease of ~ 0.6 dB of its ~ 27 dB gain for this fluence corresponding to an ionization dose of 100 krad(Si). Such a device can then survive to the radiative environments associated with both today's space missions and future more challenging applications.

In this study, we report in protons radiations damages on Europeans manufactured Commercial Of The Shelf (COTS) Light Emitting Diodes (LED). The aim of this study was to assess the potentiality of such devices for space applications. In total, fifteen references coming from three different manufacturers have been tested. All devices have been stepirradiated with 50 MeV protons, up to a fluence of 2.5E12 protons/cm². Light output, I-V characteristics and emission spectra were measured.

International audience; We present a new structure for erbium-doped optical fibers [hole-assisted carbon-coated, (HACC)] that, combined with an appropriate choice of codopants in the core, strongly enhances their radiation tolerance. We built an erbium doped fiber amplifier based on this HACC fiber and characterize its degradation under γ-ray doses up to 315 krad(SiO2) in the ON mode. The 31 dB amplifier is practically radiation insensitive, with a gain change of merely −2.2 × 10−3 dB∕krad. These performances authorize the use of HACC doped fibers and amplifiers for various applications in environments associated with today's missions (of doses up to 50 krad) and even for future space missions associated with higher dose constraints.

We present a new class of Erbium-doped optical fibers: the Hole-Assisted Carbon-Coated, HACC fibers. Optical fibers with this particular structure have been made by iXFiber on the basis of an appropriate choice of codopants in their core and claddings. By using an additional pre-treatment with deuterium (D2) loading authorized by the HACC structure, we highlight the efficiency of such components and demonstrated that this new type of fiber presents a strongly enhanced radiation resistance compared to the other types of erbium-doped optical fibers studied in litterature. We also built an Erbium-doped Fiber Amplifier (EDFA) with one of these HACC fibers and compared its radiation response to the one of the same fiber composition but without the HACC structure and D2 loading. We tested the performances of this EDFA under Υ-rays and characterize its gain degradation up to doses of 315 krad. Before irradiation, the amplifier presents a gain of about 31 dB that is comparable to the optical performances of amplifiers based on HACC fibers without the D2 pre-treatment and the HACC structure. During irradiation, our results demonstrate that the tested amplifier is nearly unaffected by radiations. Its gain slowly decreases with the dose at a slope rate of about -2.2×10-3 dB/krad. This strong radiation resistance (enhancement of a factor of ×10 compared to the previous or conventional radiation tolerant EDFA) will authorize the use of HACC doped fibers and amplifiers for various applications in space for missions associated both with low or large irradiation doses.