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Proceedings Paper

Long period and fiber Bragg gratings written within the same fiber for sensing purposes
Author(s): F. Baldini; M. Brenci; F. Chiavaioli; R. Falciai; A. Giannetti; M. Mugnaini; C. Trono
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Paper Abstract

Long period gratings (LPGs) have been recently proposed as sensing elements of chemical/biological compounds, exploiting their sensitivity to the refractive index changes in the surrounding environment. One of the difficulties of their utilization for this purpose is their strong dependence also to strain and temperature effects. An intrinsic optical feedback able to eliminate these effects was developed by manufacturing on the same fiber the LPG and a fiber Bragg grating (FBG) which is immune from external refractive index changes and is influenced by strain and temperature. An accurate temperature measurement system is utilised to eliminate or in any case to reduce to a minimum the interferences coming from temperature changes. A KrF excimer laser is used to write both the gratings into the same photosensitive fiber. The period of the LPG and FBG gratings are 615 μm and 530 nm, respectively and the attenuation at their resonance wavelengths (1570 nm for LPG and 1534 nm for FBG) was of the order of 15-20 dB. The same source, a broadband superluminescent diode with emission peak at 1550 nm, is used to interrogate both the gratings. The transmission spectra is acquired by means of an optical spectrum analyzer (OSA) controlled by a PC and an in-house software identifies the attenuation band in the FBG and LPG transmission spectra and calculates the minimum values. A suitable thermostabilized flow cell with a volume of 50 μL containing the fiber with the two gratings, has been developed and characterized.

Paper Details

Date Published: 18 January 2011
PDF: 6 pages
Proc. SPIE 7941, Integrated Optics: Devices, Materials, and Technologies XV, 794112 (18 January 2011); doi: 10.1117/12.873796
Show Author Affiliations
F. Baldini, Istituto di Fisica Applicata Nello Carrara, CNR (Italy)
M. Brenci, Istituto di Fisica Applicata Nello Carrara, CNR (Italy)
F. Chiavaioli, Univ. degli Studi di Siena (Italy)
R. Falciai, Istituto di Fisica Applicata Nello Carrara, CNR (Italy)
A. Giannetti, Istituto di Fisica Applicata Nello Carrara, CNR (Italy)
M. Mugnaini, Univ. degli Studi di Siena (Italy)
C. Trono, Istituto di Fisica Applicata Nello Carrara, CNR (Italy)


Published in SPIE Proceedings Vol. 7941:
Integrated Optics: Devices, Materials, and Technologies XV
Jean Emmanuel Broquin; Gualtiero Nunzi Conti, Editor(s)

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