143 research outputs found
Transient and Steady State Radiation Responses of Solarization-Resistant Optical Fibers
No full textInternational audienc
Coupled experiment/simulation approach for the design of radiation-hardened rare-earth doped optical fibers and amplifiers
No full textWe developed an approach to design radiation-hardened rare earth -doped fibers and amplifiers. This methodology combines testing experiments on these devices with particle swarm optimization (PSO) calculations. The composition of Er/Yb-doped phosphosilicate fibers was improved by introducing Cerium inside their cores. Such composition strongly reduces the amplifier radiation sensitivity, limiting its degradation: we observed a gain decreasing from 19 dB to 18 dB after 50 krad whereas previous studies reported higher degradations up to 0°dB at such doses. PSO calculations, taking only into account the radiation effects on the absorption efficiency around the pump and emission wavelengths, correctly reproduce the general trends of experimental results. This calculation tool has been used to study the influence of the amplifier design on its radiation response. The fiber length used to ensure the optimal amplification before irradiation may be rather defined and adjusted to optimize the amplifier performance over the whole space mission profile rather than before integration in the harsh environments. Both forward and backward pumping schemes lead to the same kind of degradation with our active fibers. By using this promising coupled approach, radiation-hardened amplifiers nearly insensitive to radiations may be designed in the future
Radiation hardening techniques for rare-earth based optical fibers and amplifiers
No full textEr/Yb doped fibers and amplifiers have been shown to be very radiation sensitive, limiting their integration in space. We present an approach including successive hardening techniques to enhance their radiation tolerance. The efficiency of our
approach is demonstrated by comparing the radiation responses of optical amplifiers made with same lengths of different rare-earth doped fibers and exposed to gamma-rays. Previous studies indicated that such amplifiers suffered significant degradation for doses exceeding 10 krad. Applying our techniques significantly enhances the amplifier radiation resistance, resulting in a very limited degradation up to 50 krad. Our optimization techniques concern the fiber composition, some possible pre-treatments and the interest of simulation tools used to harden by design the amplifiers.
We showed that adding cerium inside the fiber phosphosilicate-based core strongly decreases the fiber radiation
sensitivity compared to the standard fiber. For both fibers, a pre-treatment with hydrogen permits to enhance again the fiber resistance. Furthermore, simulations tools can also be used to improve the tolerance of the fiber amplifier by
helping identifying the best amplifier configuration for operation in the radiative environment
Radiation Response of Optical Fibers Loaded with Molecular Oxygen
No full textInternational audienceWe report an experimental investigation regarding the radiation response of Pure-Silica-Core (PSC) and F-doped Optical Fibers (OFs) previouslysubjected to a high pressure O2 loading thermal treatment. First, by micro-Raman spectroscopy we demonstrate the efficiency of the O2 loadingtechnique we applied. In particular, we showed that high concentrations (~2·10E18 molecules/cm3) of molecular oxygen are incorporated in thewhole OF cross section, almost reaching a saturation condition of the samples. Afterwards, we studied the effects of the O2 loading treatment onthe radiation response of the OFs. For this purpose we carried out a comparative study based on simultaneous online Radiation Induced Attenuation (RIA) measurements of the O2 loaded and unloaded OFs in the UV-Visible spectral domain [1]. The experiments were performed by irradiating with 10keV X-rays. The RIA spectra clearly show a strong impact of the O2 excess. The loading treatment causes an increase of the radiation sensitivity of the OFs in the UV-Visible domain.The presence of radiation induced interstitial ozone molecules is also inferred by decomposition of the RIA spectra. The information gained with the RIA experiments is further supported by Electron Paramagnetic Resonance measurements performed on γ-irradiated samples. As a radiationhardening effect it is found that the irradiation induces a ten time lower concentration of E’(Si) centers in the O2-loaded OFs.Another interesting phenomenon detected int he O2-loaded OFs is related to an infrared Radio-Luminescence (iRL) of O2 molecules:a sharp luminescence at 1272nm was indeed detected during irradiation by 10keV X-rays [2]. We will focus on the applicative aspects related tothis effect: the results we obtained show that the iRL is stable up to doses of 1MGy(SiO2) and is linearly dependent on the dose-rate up to themaximum investigated dose-rate of ~200kGy(SiO2)/h. On the basis of the obtained results we suggest that the iRL can be exploited for real-time, remote dosimetry in environments characterized by high radiation doses and high dose-rates.[1] D.Di Francesca, S.Agnello, S. Girard, C. Marcandella, P. Paillet, A. Boukenter, Y. Ouerdane, F. M. Gelardi, IEEE Trans.Nucl. Sci. 61, 3302 (2014).[2] D. Di Francesca, S. Girard, S.Agnello, C.Marcandella, P. Paillet, A. Boukenter, F. M. Gelardi, Y. Ouerdane, Appl. Phys. Lett. 105 ,83508 (2014)
Radiation Response of Optical Fibers Loaded with Molecular Oxygen
No full textInternational audienceWe report an experimental investigation regarding the radiation response of Pure-Silica-Core (PSC) and F-doped Optical Fibers (OFs) previouslysubjected to a high pressure O2 loading thermal treatment. First, by micro-Raman spectroscopy we demonstrate the efficiency of the O2 loadingtechnique we applied. In particular, we showed that high concentrations (~2·10E18 molecules/cm3) of molecular oxygen are incorporated in thewhole OF cross section, almost reaching a saturation condition of the samples. Afterwards, we studied the effects of the O2 loading treatment onthe radiation response of the OFs. For this purpose we carried out a comparative study based on simultaneous online Radiation Induced Attenuation (RIA) measurements of the O2 loaded and unloaded OFs in the UV-Visible spectral domain [1]. The experiments were performed by irradiating with 10keV X-rays. The RIA spectra clearly show a strong impact of the O2 excess. The loading treatment causes an increase of the radiation sensitivity of the OFs in the UV-Visible domain.The presence of radiation induced interstitial ozone molecules is also inferred by decomposition of the RIA spectra. The information gained with the RIA experiments is further supported by Electron Paramagnetic Resonance measurements performed on γ-irradiated samples. As a radiationhardening effect it is found that the irradiation induces a ten time lower concentration of E’(Si) centers in the O2-loaded OFs.Another interesting phenomenon detected int he O2-loaded OFs is related to an infrared Radio-Luminescence (iRL) of O2 molecules:a sharp luminescence at 1272nm was indeed detected during irradiation by 10keV X-rays [2]. We will focus on the applicative aspects related tothis effect: the results we obtained show that the iRL is stable up to doses of 1MGy(SiO2) and is linearly dependent on the dose-rate up to themaximum investigated dose-rate of ~200kGy(SiO2)/h. On the basis of the obtained results we suggest that the iRL can be exploited for real-time, remote dosimetry in environments characterized by high radiation doses and high dose-rates.[1] D.Di Francesca, S.Agnello, S. Girard, C. Marcandella, P. Paillet, A. Boukenter, Y. Ouerdane, F. M. Gelardi, IEEE Trans.Nucl. Sci. 61, 3302 (2014).[2] D. Di Francesca, S. Girard, S.Agnello, C.Marcandella, P. Paillet, A. Boukenter, F. M. Gelardi, Y. Ouerdane, Appl. Phys. Lett. 105 ,83508 (2014)
Radiation-resistant rare-earth-doped optical fiber and method of radiation-hardening a rare-earth-doped optical fiber
No full textRadiation-resistant rare-earth-doped optical fiber and method of radiation-hardening a rare-earth-doped optical fiber
No full textCombined temperature and radiation effects on solarization-resistant silica-based optical fibers
No full textInternational audienceWe investigated the combined effects of steady state irradiation and temperature on the transmission properties in the UV-visible spectral domain of a solarization-resistant (SR) multimode fiber from Polymicro. Nature, growth, decay kinetics and temperature dependencies of the Si-related defects involved in the fiber degradation are introduced
Combined temperature and radiation effects on solarization-resistant silica-based optical fibers
No full textInternational audienceWe investigated the combined effects of steady state irradiation and temperature on the transmission properties in the UV-visible spectral domain of a solarization-resistant (SR) multimode fiber from Polymicro. Nature, growth, decay kinetics and temperature dependencies of the Si-related defects involved in the fiber degradation are introduced
Pulsed X‐Ray Radiation Responses of Single‐Mode and Multimode Fluorine‐Doped Optical Fibers
No full textInternational audienceIn this study, we compare the pulsed X‐ray radiation responses of standard, radiation‐tolerant optical fibers with those of super‐hard, radiation‐resistant multimode (MM‐SRH) and single‐mode (SM‐SRH) fluorine‐doped optical fibers. Real‐time measurements of radiation‐induced attenuation (RIA) spectra were conducted in the spectral range of 0.6 to 3.0 eV (400–2000 nm), both at room temperature and at liquid nitrogen temperature, to characterize the nature of metastable defects, quickly recombining after the short (a few tens of ns) irradiation pulse. Additionally, we monitored the RIA kinetics at the two telecommunication wavelengths, 1550 and 1310 nm, from the microsecond timescale to several hundreds of seconds. MM‐SRH fibers exhibit superior light transmission efficiency following the X‐ray irradiation pulse, better than the other fiber compositions and the one expected from current literature on transient responses of silica‐based optical fibers. Possible explanation of this radiation hardness could be the very high level F‐doping distribution in this graded‐index optical fiber, demonstrating how the RIA in optical fibers strongly depends on fiber composition and manufacturing parameters
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