Fiber modal Michelson interferometers with coherence addressing and heterodyne interrogation

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 ar...

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Bibliographic Details
Published in:Optical Engineering 2008-04, Vol.47 (4), p.044401-044407
Main Authors: Caldas, Paulo, Jorge, Pedro A. S, Arau´jo, F. M, Ferreira, Lui´s A, Marques, Manuel B, Rego, Gaspar, Santos, Jose´ Lui´s
Format: Article
Language:English
Subjects:
Coherence
coherence addressing
Fiber optics
Fibers
heterodyne interrogation
Interferometers
Interrogation
long-period grating
modal interferometer
Optical fibers
Refractive index
Refractivity
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Summary: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 down to 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.
ISSN:0091-3286
1560-2303
DOI:10.1117/1.2903089