Transient Radiation Responses of Optical Fibers: Influence of MCVD Process Parameters

Abstract

International audienceA dedicated set of fibers elaborated via the Modified Chemical Vapor Deposition (MCVD) technique is used to study the influence of composition and drawing parameters on their responses to an X-ray pulse representative of the radiation environments associated with Megajoule class lasers. These canonical fibers were designed to highlight the impact of these parameters on the amplitude and kinetics of the transient pulsed X-ray Radiation Induced Attenuation (RIA) at room temperature. From preforms differing by their core composition, three optical fibers were elaborated by varying the tension and speed during the drawing process. No or only slight RIA change results from the tested variations in drawing process parameters of Ge-doped, F-doped, and pure-silica-core fibers. This study reveals that the drawing process is not the main parameter to be optimized in order to enhance the radiation tolerance of MCVD specialty optical fibers for the LMJ harsh environment. From the hardness assurance point of view, a specialty fiber sufficiently tolerant to this environment should be robust against changes in the drawing process. The origins of the RIA observed in the different fibers are discussed on the basis of spectral decomposition of their measured RIA spectra, using sets of defects from the literature and related to the different core dopants. This analysis highlights the limits of the well-known defect set to reproduce the RIA above 1 $mu{rm m}$ for Ge-doped fibers whereas self-trapped holes and chlorine-related species seem responsible for the transient responses of pure-silica-core and F-doped fibers

Influence of <formula formulatype="inline"><tex Notation="TeX">${\hbox{O}}_2$</tex></formula>-Loading Pretreatment on the Radiation Response of Pure and Fluorine-Doped Silica-Based Optical Fibers

“…7 clearly show a higher absorption at about 3.5 eV of Cl-related defects in the F2D3-O2 sample compared with the F2D3. Whether the absorption band is assigned to Cl or Cl [19], [24], the mechanism suggested for the generation of Cl atoms is…”

“…7(c), we report the decomposition of the difference of the two previous spectra. By comparing the II OPTICAL CHARACTERISTICS OF RADIATION-INDUCED ABSORPTION BANDS [1], [16], [17], [18], [19], [20], [21], [22] Required and used only for the fitting of F2D3-O2. From Reference [21] The spectral parameters fall within the variability of the values reported in literature.…”

The Relevance of Point Defects in Studying Silica-Based Materials from Bulk to Nanosystems

“…Common procedures to realize low SiOH silica bulks and preforms for optical fibers, such as the MCVD (modified chemical vapor deposition) technique, can introduce Cl impurities in the matrix [7,56]. As a consequence of the chlorine presence, Cl-related absorbing defects are induced during irradiation [56][57][58][59][60][61]. Although the specific nature of such defects should be further investigated, the presence of such absorption can represent a limitation in optical fiber applications such as in ITER (International Thermonuclear Experimental Reactor) and Laser Megajoule (LMJ) [61].…”

“…As a consequence of the chlorine presence, Cl-related absorbing defects are induced during irradiation [56][57][58][59][60][61]. Although the specific nature of such defects should be further investigated, the presence of such absorption can represent a limitation in optical fiber applications such as in ITER (International Thermonuclear Experimental Reactor) and Laser Megajoule (LMJ) [61]. While such procedures, introducing Cl, are good solutions for telecom fibers, they may not be the optimal choice for other applications.…”

Прогнозирование Радиационно-Наведенного Поглощения Света В Волоконных Световодах С Сердцевиной Из Нелегированного Кварцевого Стекла В Космических Применениях

“…Ранее установлено, что РЦО в ВС с сердцевиной из нелегированного SiO 2 при космических дозах (< 10 Gy) могут быть обусловлены двумя факторами: деформациями сетки стекла ВС и наличием в ней примеси хлора [7][8][9][10]. Хлорный РЦО имеет максимум РНП в ультрафиолетовой области, а деформационные РЦОв видимой области, при этом хвосты и тех и других РЦО и создают значительное РНП и на λ = 1.55 µm.…”