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Proceedings Paper

Core-cladding interface disturbances during the collapsing processis one of the origins of optical losses in heavily doped fibers
Author(s): A. S. Biriukov; Eugeni M. Dianov; Andrey S. Kurkov; A. G. Khitun; Grigory G. Devyatykh; Alexei N. Guryanov; D. D. Gusovskii; S. V. Kobis
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Paper Abstract

It is well known that fibers with a high index difference between the core and the cladding have additional optical losses, which can not be explained by the known sources. In the case of fibers with a germanosilicate core these losses can achieve several dB/kin for a germanium dioxide concentration of 20-30 mol.%. For fibers with an alumosilicate core additional losses amount to 10-30 dB/km. We believe that one of the origins of the loss increase consist in the interpenetrating of the core and cladding materials at their boundary. This phenomenon takes place in preforms produced by inside vapor deposition, if the viscosities of the cladding and the core glasses are different because of a high level of the core doping. During the collapsing process the boundary of two liquids with the different viscosities can lose stability leading to the material interpenetrating. As the result, so called "viscous fingers" arise along the core-cladding boundary. It is easy to observe these formations in preforms with an alumosilicate core, where the characteristic length of "viscous fingers" is comparable with the core diameter study of the core-cladding interface instability. The main point of the theoretical consideration is the eigen oscillation frequencies of the core-cladding boundary. The study is based on the model of contact of two cylindrical layers of liquids with different viscosities. It is shown th In this paper we present the results of a theoretical and experimental at there is a set of eigen oscillation frequencies such that perturbations at these frequencies are not damped out with time. Also, we have found the frequencies resulting in the fastest increase of the perturbations. For the preforms with an alumosilicat core the simulated results and the number of the observed "viscous fingers" are in a satisfactory agreement. It follow from this investigation that the stability of the core-cladding interface can be improved by using special co-dopants. These co-dopants should change the composition of the two contacting glasses (or one of them) so as to match their viscosities.

Paper Details

Date Published: 2 January 1998
PDF: 6 pages
Proc. SPIE 3211, International Conference on Fiber Optics and Photonics: Selected Papers from Photonics India '96, (2 January 1998); doi: 10.1117/12.345541
Show Author Affiliations
A. S. Biriukov, Russian Academy of Sciences (Russia)
Eugeni M. Dianov, Russian Academy of Sciences (Russia)
Andrey S. Kurkov, General Physics Institute (Russia)
A. G. Khitun, General Physics Institute (Russia)
Grigory G. Devyatykh, Institute of Chemistry of High-Purity Substances of the Academy of Science (Russia)
Alexei N. Guryanov, Institute of Chemistry of High-Purity Substances of the Academy of Sciences (Russia)
D. D. Gusovskii, Institute of Chemistry of High-Purity Substances of the Academy of Sciences (Russia)
S. V. Kobis, Institute of Chemistry of High-Purity Substances (Russia)


Published in SPIE Proceedings Vol. 3211:
International Conference on Fiber Optics and Photonics: Selected Papers from Photonics India '96
J. P. Raina; P. R. Vaya, Editor(s)

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