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Proceedings Paper

Bend insensitive long-period gratings written with a CO2 laser in fiber with parabolic-index cladding
Author(s): Filip Todorov; Miroslav Chomát; Daniela Berková; Jirí Ctyroký; Vlastimil Matejec; Ivan Kašík; Jirí Dunovský; Alexandr Jancárek
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Paper Abstract

Bending characteristics of long-period gratings (LPGs) written in fiber with parabolic-index cladding are investigated experimentally. The fiber has a uniform outer cladding and an inner cladding, where the refractive index decreases quadratically with radius. A recent theoretical analysis has shown that these LPGs can be highly insensitive to bending. A very small bend-induced wavelength shift of the attenuation band of only 5 nm was predicted for an LPG bent with a uniform curvature of 100 m-1. Experiments to prove the predicted bend insensitivity are done with LPGs written with a CO2 laser at one-side and three-side laser irradiation of the fiber. The LPG is bent in an arrangement, where the curvature is maximum in the LPG's center and decreases linearly along the bent LPG in both directions. Bend-induced wavelength shifts of an attenuation band appearing at about 1560 nm and attributed to coupling between the fiber modes LP01 and LP02, are examined for four rotational orientations of the LPG inscribed at three-side laser irradiation. The largest shift of 0.46 nm is obtained for a maximum curvature (in the middle of the LPG) of 11.6 m-1, (or average curvature of 5.8 nm-1) corresponding to the largest deflection applied on the LPG in the experiments. The depths of the bands of the above LPG at the -5.5-dB level are observed to vary by less than 0.3 dB over the whole range of applied curvatures.

Paper Details

Date Published: 26 November 2007
PDF: 8 pages
Proc. SPIE 6830, Advanced Sensor Systems and Applications III, 683005 (26 November 2007); doi: 10.1117/12.756314
Show Author Affiliations
Filip Todorov, Institute of Photonics and Electronics (Czech Republic)
Czech Technical Univ. in Prague (Czech Republic)
Miroslav Chomát, Institute of Photonics and Electronics (Czech Republic)
Daniela Berková, Institute of Photonics and Electronics (Czech Republic)
Jirí Ctyroký, Institute of Photonics and Electronics (Czech Republic)
Vlastimil Matejec, Institute of Photonics and Electronics (Czech Republic)
Ivan Kašík, Institute of Photonics and Electronics (Czech Republic)
Jirí Dunovský, Czech Technical Univ. in Prague (Czech Republic)
Alexandr Jancárek, Czech Technical Univ. in Prague (Czech Republic)


Published in SPIE Proceedings Vol. 6830:
Advanced Sensor Systems and Applications III
Yun-Jiang Rao; Yanbiao Liao; Gang-Ding Peng, Editor(s)

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