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Infrared radiation Induced attenuation of radiation sensitive optical fibers: influence of temperature and modal propagation
摘要： We investigate the X-ray (40 keV) and γ-ray (1.2 MeV) radiation responses of three different radiation sensitive Optical Fibers (OFs) up to 100 Gy(SiO2). In particular, we study the Radiation Induced Attenuation (RIA) in the Near Infrared domain (NIR) for single mode OFs doped with Phosphorus (P), Aluminum (Al) and Phosphorus/Cerium (PCe) in their cores at three temperatures up to 50 °C. RIA levels and kinetics strongly depend on the operating wavelength and fiber composition. For both P and PCe-doped fibers, the P1 defects are the main contributors to the RIA, with Ce-codoping inducing a decrease of radiation sensitivity. For the Al-doped fiber, no specific absorption bands can be discriminated in the NIR. Both X- and γ-rays lead to the same RIA levels and kinetics. The RIA spectral dependences on dose and temperature highlight the potential of the three investigated fibers for radiation detection and dosimetry. To better discuss the properties of point defects responsible for the NIR RIA, we analyze how the fundamental mode propagation influences the RIA spectra of each fiber type. By reasonably assuming that the core RIA exceeds largely the cladding RIA and by calculating the mode Confinement Factor (CF), the RIA spectra of the core material are reconstructed and the spectral characteristics of defects are discussed for each type of fibers.
关键词： Radiation Induced Attenuation,Aluminum,Optical fiber,Phosphorus,Cerium
更新于2025-09-23 15:19:57
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Radiation induced attenuation in pure silica polarization maintaining fibers
摘要： Radiation-induced attenuation (RIA) at λ = 1.55 μm is studied in polarization-maintaining (PM) pure-silica-core optical fibers of the Panda-type under γ-irradiation and upon pulsed-X-ray-irradiation. For the first time, the RIA spectrum is compared under γ-irradiation in a Panda and in a non-PM fiber drawn from the same preform before embedding the stress-applying rods. It is found out that the chief RIA origins in the near-IR range in both fibers are an extremely short-lived band centered at ~1 eV and the tails of the classical bands due to strain-assisted self-trapped holes (STHs) at 1.63 and 1.88 eV. The former band is found to be many times more intense in the Panda; the latter bands, somewhat more intense in the non-PM fiber. The ~1-eV band proved to be composed of two Gaussian sub-bands centered at 0.95 and 1.12 eV. Under γ-irradiation, the composite ~1-eV band is found to be photobleached virtually fully by 1.55-μm light of 5-mW power, which results in manifold reduction of the total RIA. Upon pulsed irradiation, RIA in Pandas at large post-pulse times (> 1 ms–1 s) is found to fall off below the record low level demonstrated elsewhere by a non-PM pure-silica-core fiber. This fact is explained as being due to a smaller concentration of strain-assisted STHs in Pandas than in non-PM fibers. The concentration of strain-assisted STHs in Pandas is shown to increase with increasing the value of birefringence.
关键词： Radiation-induced attenuation,Self-trapped holes,Polarization-maintaining fiber
更新于2025-09-19 17:15:36
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Implementation of Optical Fiber Post-Mortem Dose Measurements: a Proof of Concept
摘要： We describe the implementation of a versatile system and corresponding method to perform fast post-mortem optical attenuation measurements on irradiated Optical Fibers (OFs) for dosimetry purposes. The measurement is based on the Radiation Induced Attenuation (RIA) phenomenon. We employ a dual wavelength Optical Time Domain Reflectometer (OTDR) coupled with a suitable radiation sensitive OF. We demonstrate that radiation dose levels higher than 100 Gy(SiO2) can be measured efficiently with 1 m long samples. The accuracy of the measurement increases with the increasing radiation dose if the length of the sample is kept fix. We also highlight possible limitations of our approach and, more generally, limitations related to perform accurate RIA measurement (online or post-mortem) on short single mode OF samples. The technological solution we propose can be tailored to address different radiation environment.
关键词： Optical fibers,P-doped,radiation sensitive,Dosimetry,Radiation Induced Attenuation,CERN
更新于2025-09-11 14:15:04
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Effect of Temperature and Gamma-Ray Irradiation on Optical Characteristics of Fiber Bragg Grating Inscribed Radiation-Resistant Optical Fiber
摘要： A new radiation-hard germano-silicate glass optical fiber with a pure silica glass buffer and a boron-doped silica glass inner cladding was fabricated for temperature sensor application based on the fiber Bragg grating (FBG) under γ-ray irradiation environment. The temperature dependences of optical attenuation at 1550.5 nm and Bragg reflection wavelength shift from 18 ℃ to 40 ℃ before the γ-ray irradiation were about 4.57×10–4 dB/℃ and 5.48 pm/℃, respectively. The radiation-induced optical attenuation at 1550.5 nm and the radiation-induced Bragg reflection wavelength shift under the γ-ray irradiation with the total dose of 22.85 kGy at 35 ℃ were about 0.03 dB/m and 0.12 nm, respectively, with the γ-ray irradiation sensitivity of 5.25×10–3 pm/Gy. The temperature and the γ-ray irradiation dependence of optical attenuation at 1550.5 nm in the FBG written fiber with boron-doped silica glass inner cladding were about 6 times and 4 times lower than that in the FBG written fiber without boron-doped silica glass inner cladding under a temperature change from 18 ℃ to 40 ℃ and the γ-ray irradiation with the total dose of 22.85 kGy at 35 ℃, respectively. Furthermore, the effect of temperature increase on the Bragg reflection wavelength of the FBG written fiber with boron-doped silica inner cladding was much larger about 1000 times than that of the γ-ray irradiation. However, no influence on the reflection power of the Bragg wavelengths and the full width at half maximum (FWHM) bandwidth under temperature and the γ-ray irradiation change was found. Also, after the γ-ray irradiation with the dose of 22.85 kGy, no significant change in the refractive index was found but the residual stresses developed in the fiber were slightly relaxed or retained.
关键词： Optical fiber,radiation-induced attenuation,fiber Bragg grating,temperature sensor,radiation resistance
更新于2025-09-11 14:15:04