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Temperature as a function of time measured at fixed irradiation temperature ( ) during irradiation and recovery period for SMF-A1 pre-treated. Black circles indicate temperature calculated by Rayleigh measurements in the non-irradiated zone, green circles represent temperature values in the irradiated part of the sample; the red line is the temperature measured by the thermocouple.
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We study the performance of Optical Frequency Domain Reflectometry (OFDR) distributed temperature sensors using radiation resistant single-mode optical fibers. In situ experiments under 10 keV X-rays exposure up to 1 MGy(SiO2) were carried out with an original setup that allows to investigate combined temperature and radiation effects on the sensor...
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Context 1
... Measurement Procedure: To investigate the transient ef- fects on Rayleigh response we performed two types of experi- ments. The first, at fixed irradiation temperature ( ), is designed to evaluate the OBR response during both irradia- tion and recovery stages; an example of acquired data is shown in Fig. 3. Fig. 3 shows obtained results in fixed experiments. These results will be summarized in terms of between irradiated and non-irradiated part at the end of irradiation. Comparison with thermocouple data is achieved to demonstrate that temper- ature is well estimated by OBR. We note however that during the recovery the temperatures ...
Context 2
... Measurement Procedure: To investigate the transient ef- fects on Rayleigh response we performed two types of experi- ments. The first, at fixed irradiation temperature ( ), is designed to evaluate the OBR response during both irradia- tion and recovery stages; an example of acquired data is shown in Fig. 3. Fig. 3 shows obtained results in fixed experiments. These results will be summarized in terms of between irradiated and non-irradiated part at the end of irradiation. Comparison with thermocouple data is achieved to demonstrate that temper- ature is well estimated by OBR. We note however that during the recovery the temperatures differ ...
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Citations
... Radiation can also affect coating layers outside optical fibers. A series of studies by Rizzolo and coworkers has shown that both temperature and radiation exposure could modify the elastic properties of several types of coating, or the interface between fiber and coating [39][40][41][42]. These changes are manifested in distributed temperature measurements through optical frequency domain reflectometry (OFDR), and may alter their proper calibration [39][40][41][42]. ...
... A series of studies by Rizzolo and coworkers has shown that both temperature and radiation exposure could modify the elastic properties of several types of coating, or the interface between fiber and coating [39][40][41][42]. These changes are manifested in distributed temperature measurements through optical frequency domain reflectometry (OFDR), and may alter their proper calibration [39][40][41][42]. Pre-treatments of temperature cycles or radiation exposure were proposed and established to reduce such inaccuracies [39][40][41][42]. ...
... These changes are manifested in distributed temperature measurements through optical frequency domain reflectometry (OFDR), and may alter their proper calibration [39][40][41][42]. Pre-treatments of temperature cycles or radiation exposure were proposed and established to reduce such inaccuracies [39][40][41][42]. Possible weakening of the coatings themselves was investigated as well [43]. ...
The monitoring of ionizing radiation is critical for the safe operation of nuclear and other high-power plants. Fiber-optic sensing of radiation has been pursued for over 45 years. Most protocols rely on radiation effects on the optical properties of the fiber. Here we propose a new concept, in which the opto-mechanics of standard fibers coated by thin layers of fluoroacrylate polymer are observed instead. The time-of-flight of radial acoustic waves through the coating is evaluated by forward stimulated Brillouin scattering measurements. The time-of-flight is seen to decrease monotonically with the overall dosage of gamma radiation from a cobalt source. Variations reach 15% of the initial value for 180 Mrad dose and remain stable for at least several weeks following exposure. The faster times-of-flight are consistent with a radiation-induced increase in the coating stiffness, observed in offline analysis. The effects on the coating are independent of possible changes in the optical parameters of the fiber. The combination of opto-mechanical analysis together with established fiber sensing protocols may help disambiguate the evaluation of multiple radiation metrics and reduce environmental cross-sensitivities. The technique is suitable for online monitoring and may be extended to spatially distributed measurements.
... Sensors 2020, 20, 4129 2 of 12 optical fiber sensors that operate in the ionizing radiation field [13] have been extensively studied in order to define and understand the effects of radiation on their properties [14,15]. Investigations have focused on off-line and real-time monitoring, to assess ionizing radiation sensitivity of in-fiber devices and to correlate their response with the radiation dose [16,17]. ...
In this work, we present a new setup for real-time investigations of optical fibers and optical fiber sensors while being subjected to gamma-rays. The investigation of the radiation effects on novel or well-assessed sensing devices has attracted a lot of interest, however, the facilities required to do this (when available) are barely accessible to the device to be characterized. In order to reduce the limitations of these types of experiments and ensure a highly controlled environment, we implemented a configuration that permits the on-line testing of optical components inside a Co-60 gamma chamber research irradiator. To show the advantages of this new approach, we present a case study that compares an arc-induced optical fiber long period grating (LPG) irradiated in a gamma chamber with the same type of grating irradiated with gamma-rays from a Co-60 industrial irradiator. In order to better understand the effects of radiation on such components and their behavior in radiation environments, we focus on the homogeneity of the radiation field and parameter customizability as well as the high reproducibility of the experiments.
... -La température mesurée par l'instrument Rayleigh OFDR (sur des échantillons de 10 m de longueur de fibres PSC et dopée F) et les coefficients de déformation restent stables et constants après des irradiations allant jusqu'à 10 MGy de dose accumulée [74]. ...
... Toutes les mesures du décalage spectral en fonction de la température peuvent être résumées par l'évolution de leurs coefficients de température par rapport à la dose d'irradiation pour toutes les fibres testées. Pour chaque palier de contrainte de chaque échantillon (20,74,131,195 ...
Cette thèse a été réalisée en collaboration entre l'Andra (L’Agence Nationale pour la Gestion des Déchets Radioactifs) et le laboratoire Hubert Curien (Unité Mixte de Recherche CNRS 5516) de l’Université Jean Monnet de Saint-Étienne. Dans ce travail, j’ai évalué les performances de capteurs à fibre optique pour la surveillance du site de stockage géologique de déchets radioactifs à vie longue (projet Cigéo). Cette application demande un suivi régulier, déporté et réparti de l’évolution de différentes grandeurs d’intérêt telles que : la température, la déformation et la présence d’hydrogène (ainsi que leurs combinaisons) en environnement radiatif sévère. La solution proposée repose sur les suivis des évolutions des signatures optiques de ces guides via des études en rétrodiffusion : Brillouin, Rayleigh et Raman. Afin de répondre à cette problématique, plusieurs systèmes d’interrogations ont été testés (utilisés). Selon leurs spécificités, ils se différencient par leurs types d’analyses, leurs résolutions spatiales, leurs budget optique et portées…. La sélection des fibres optiques d’étude est un élément clés pour ce type d’applications car elles doivent résister à ces environnements extrêmes sur de longues durées. Dans ce travail, j’ai étudié les réponses de fibres optiques contenant différents dopants, en particulier Ge et F. J’ai quantifié les effets des rayonnements gamma, de la température, de la déformation et de la présence d'hydrogène sur la qualité des mesures réparties. En conclusion, mon travail a cerné le type de fibre optique à utiliser pour ces environnements sévères. Les interrogateurs conditionnent le type de fibre à utiliser ainsi que leurs longueurs et, par conséquent, permettent de bien cerner les dimensions des zones à surveiller. Les qualités des résultats de mesures sont gouvernées par les choix de plusieurs paramètres et notamment : la durée de l’impulsion, la puissance injectée dans la fibre, les pas fréquentiels, la durée de la mesure…qui se répercutent directement sur les résolutions finales (spatiales et fréquentielles) des grandeurs mesurées. Une attention particulière doit être attachée à ces critères.
... The radiation and temperature coupled effect has been already studied for X-rays on different fibers in [9] but never for strain sensing based on Brillouin or Rayleigh scatterings. The coupled influence of X-ray radiation and temperature was already analyzed for temperature sensing via Rayleigh scattering in [10,14]. In [15] we briefly started to evaluate the coupled effect on Brillouin scattering in standard Ge-doped fibers; here we expand the study and consider also "radiation hard" fibers, F-doped, in order to evaluate the feasibility of using optical fibers as strain sensors in harsh and complex environment. ...
... The interoperability had then to be evaluated. What is more, literature is abundant for radiation impact on OBR/OFDR sensing system [10,14] and remains very limited for TW-COTDR. It is therefore useful to check if TW-COTDR behaves similarly with OBR, i.e. if results on Rayleigh scattering remain valid whatever the measuring technique. ...
Coupled temperature and γ-ray influence on Brillouin (PPP-BOTDA) and Rayleigh (TW-COTDR) scatterings are quantified. Aging tests of these distributed strain measuring systems are performed on-line, up to 1 MGy, at room temperature, 80 ∘ C, 100 ∘ C and 120 ∘ C. Brillouin and Rayleigh frequency shifts remain identical regardless of the temperature: 3 MHz (2 MHz) and 7 GHz (3 GHz) for Ge-doped (respectively F-doped) fiber at 1 MGy. Meanwhile, radiation-induced attenuation is diminished because of the higher temperature; hence, the maximal distance range is less deteriorated. These tests help to explain the origin of the Brillouin frequency shift under γ-rays, with an acoustic velocity variation of about 1 m/s in 1 MGy irradiated samples.
... Several studies have been performed to characterize the performance of Rayleigh-based sensors in radiation-rich environments. The two main categories of sensors are those based on the OTDR technique, and those operating in the frequency domain, OFDR [57,259,260,261,262]. From the available results, it seems that except for some very specific environments such as those associated with very high neutron fluences, the Rayleigh signature remains almost unaffected by radiation and that RIA reducing the fiber sensing length remains the main degradation parameter to be followed. ...
... • OFDR temperature sensors: For temperature sensing, the OFDR sensors associated with radiation hardened optical fibers are able to operate up to very high doses of γ-rays [261,262,268] and neutron fluences up to 10 17 n/cm² [17]. ...
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.
... Optical fiber sensors present clear advantages for operation in such extreme conditions. It can be used for remote measurements in environments which are hazardous or which suffer from the electromagnetic interference [6,7]. An optical fiber can act as the sensing element for a large variety of external parameters such as strain [8], temperature [9] and pressure [10], because it is able to survive to the harsh environmental constraints. ...
In this work, the optical fiber sensor system to measure the optical loss due to temperature variation of gasoline and toluene was papered. The optical fiber sensor was characterized using optical time domain reflectometer (OTDR). The sensor was a 50 cm multimode fiber with about 1–3 cm at its central region being partially unclad. The partial uncladding was carried out using chemical etching technique. The optical loss of sensor was measured when unclad part exposed to gasoline and toluene respectively at different temperature ranging from 25 °C to 60 °C. The optical loss of sensor increases in a step drop of OTDR trace as the temperature is increased. The rate of optical loss was estimated to be 0.01576 dB/°C and 0.02212 dB/°C for gasoline and toluene respectively.
... On the other hand, recent work from our group has shown that radiations at MGy dose levels do not affect the optical fibre Rayleigh signature at the basis of the OFDR technique. Indeed, temperature and strain coefficients remain unchanged, within the 5% error, up to 10 MGy for a large variety of standard fibre classes 16 and distributed temperature measurements (from −40 °C up to 250 °C) have been shown not to be influenced by radiations up to 1 MGy 17,18 . However, it has been shown that the potentialities of OFDR sensors are affected by Radiation Induced Attenuation (RIA) phenomenon 16 , which limits the sensing range of the fibre, while its packaging could modify the sensor calibration curves and consequently influences the distributed measurements 18,19 . ...
... Indeed, temperature and strain coefficients remain unchanged, within the 5% error, up to 10 MGy for a large variety of standard fibre classes 16 and distributed temperature measurements (from −40 °C up to 250 °C) have been shown not to be influenced by radiations up to 1 MGy 17,18 . However, it has been shown that the potentialities of OFDR sensors are affected by Radiation Induced Attenuation (RIA) phenomenon 16 , which limits the sensing range of the fibre, while its packaging could modify the sensor calibration curves and consequently influences the distributed measurements 18,19 . ...
... We note that the shift in temperature or strain is purely a linear scaling of the spectral frequency shift Δν for moderate temperature and strain ranges. This dependence, linked to the material properties, has been experimentally proven [14][15][16][17][18][19] and the temperature calibration reported in the experimental section (see the first figure of Distributed temperature measurements section) is a clear demonstration of it. Indeed, as explained above the spectral shift is dependent on physical length changes. ...
We present an innovative architecture of a Rayleigh-based optical fibre sensor for the monitoring of water level and temperature inside storage nuclear fuel pools. This sensor, able to withstand the harsh constraints encountered under accidental conditions such as those pointed-out during the Fukushima-Daiichi event (temperature up to 100 °C and radiation dose level up to ~20 kGy), exploits the Optical Frequency Domain Reflectometry technique to remotely monitor a radiation resistant silica-based optical fibre i.e. its sensing probe. We validate the efficiency and the robustness of water level measurements, which are extrapolated from the temperature profile along the fibre length, in a dedicated test bench allowing the simulation of the environmental operating and accidental conditions. The conceived prototype ensures an easy, practical and no invasive integration into existing nuclear facilities. The obtained results represent a significant breakthrough and comfort the ability of the developed system to overcome both operating and accidental constraints providing the distributed profiles of the water level (0–to–5 m) and temperature (20–to–100 °C) with a resolution that in accidental condition is better than 3 cm and of ~0.5 °C respectively. These new sensors will be able, as safeguards, to contribute and reinforce the safety in existing and future nuclear power plants.
... The radiation effects on Rayleigh-based sensors have been studied in France in the recent years in the frameworks of PhD theses between Andra, LabHC and AREVA [21,[73][74][75]. The same methodology as described in 0 was applied, either with OBR instrument [9] or TW-OTDR [10]. ...
This paper presents the state of the art distributed sensing systems, based on optical fibres, developed and qualified for the French Cigéo project, the underground repository for high level and intermediate level long-lived radioactive wastes. Four main parameters, namely strain, temperature, radiation and hydrogen concentration are currently investigated by optical fibre sensors, as well as the tolerances of selected technologies to the unique constraints of the Cigéo’s severe environment. Using fluorine-doped silica optical fibre surrounded by a carbon layer and polyimide coating, it is possible to exploit its Raman, Brillouin and Rayleigh scattering signatures to achieve the distributed sensing of the temperature and the strain inside the repository cells of radioactive wastes. Regarding the dose measurement, promising solutions are proposed based on Radiation Induced Attenuation (RIA) responses of sensitive fibres such as the P-doped ones. While for hydrogen measurements, the potential of specialty optical fibres with Pd particles embedded in their silica matrix is currently studied for this gas monitoring through its impact on the fibre Brillouin signature evolution.
... Andra's interest focuses on distributed sensing because of its complementarity to strain gauges and platinum probes. The potential of Brillouin 2 , Rayleigh 3,4,5,6,7 and Raman 8 scattering responses in harsh environments has been studied over the last decade 9,10 . Raman based sensing allows the monitoring of the sole temperature parameters and combination with Brillouin or Rayleigh sensors is usually needed to discriminate between temperature and strain. ...
... Where C T and Cε are the fiber temperature and strain calibration coefficients with typical values of 1.5 GHz/°C and 0.15 GHz/µε for Telecom-grade single mode fibers (SMFs). These values depend on the fiber type, mainly through its core and coating composition ... For a literature coherence effort with available OFDR results 3,4,5,6 , this equation can be divided by the mean frequency ʋ. The coefficients become 7.75×10 -6 °C -1 and 0.78 µε-1 respectively. ...
... Raman sensors have been shown to be sensitive to the RIA used to evaluate the temperature along the sensing fiber, which, if not corrected [3], is responsible of huge errors on temperature responses of single-ended systems. Recent results have shown that Rayleigh sensors are more robust against total ionizing dose (TID): the temperature and strain coefficients are not affected nor by permanent effects up to at least 10 MGy(SiO2) irradiation dose [4] either by steady-state irradiation up to, at least, 1 MGy(SiO2) [5]. Nevertheless, fiber packaging influences the OFDR sensor response: radiation changes the mechanical properties of the coating surrounding the fiber core/cladding and can lead to errors in strain or temperature distributed measurements. ...
... The purpose of this work is to study the response of fluorine doped single mode fiber as OFDR-based sensor in mixed and neutron environments. This radiation hardened optical fiber shows good OFDR sensing properties at MGy dose levels and for irradiation temperature range of [30 °C -100 °C] [5]. ...
We report the study of a radiation resistant single mode optical fiber doped with fluorine exposed to mixed neutron and γ-radiation up to 1017 n/cm² fluence and > 2 MGy dose to evaluate its performances when used as the sensing element of a distributed Optical Frequency Domain Reflectometry (OFDR). The use of complementary spectroscopic techniques highlights some differences between the responses of solely γ-radiation (10 MGy) or mixed neutron and γ (1017 n/cm² + >2 MGy) irradiated samples. Those differences are linked to the defect generation rather than to structural changes of the a-SiO2 host matrix. We show that a modification of the refractive index of ~10-5 is induced at the highest investigated neutron fluence. However, the feasibility of distributed temperature measurements along the irradiated fiber is demonstrated with an accuracy of 0.1 °C over a sensing length up to ~130 m with the tested OBR4600 interrogator. These results are very promising for the integration of OFDR sensors in mixed neutron and gamma radiation environments.
