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Optical Engineering

Fiber modal Michelson interferometers with coherence addressing and heterodyne interrogation
Author(s): Paulo Caldas; Pedro A. S. Jorge; F. M. Araujo; Luís Alberto Ferreira; M. B. Marques; Gaspar M. Rego; José Luís Santos
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Paper Abstract

A long-period-grating-based fiber optic Michelson modal interferometer with coherence addressing and heterodyne interrogation is studied as a sensing structure for measuring environmental refractive index, temperature, and liquid level. The effects of several system parameters on the measurements are investigated. Experimental results show that the sensitivity to the external refractive index increases with the order of cladding mode and with a reduction of the fiber diameter. The decrease of the fiber diameter from 125 µm down to 70 μm enhances the sensitivity to the external index by a factor of 2.7. It is also shown that the use of a silica-core fiber increases the sensitivity to the external index by a factor of 1.4 and reduces the thermal sensitivity by a factor of 2.5 compared to a standard fiber.

Paper Details

Date Published: 1 April 2008
PDF: 7 pages
Opt. Eng. 47(4) 044401 doi: 10.1117/1.2903089
Published in: Optical Engineering Volume 47, Issue 4
Show Author Affiliations
Paulo Caldas, INESC Porto (Portugal)
Pedro A. S. Jorge, INESC Porto (Portugal)
F. M. Araujo, INESC Porto (Portugal)
Luís Alberto Ferreira, FiberSensing - Sistemas Avançados de Monitorização, S.A. (Portugal)
M. B. Marques, INESC Porto (Portugal)
Gaspar M. Rego, Instituto Politécnico de Viana do Castelo (Portugal)
José Luís Santos, Univ. do Porto (Portugal)

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