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Proceedings Paper

Demonstration of a dual-cavity extrinsic fiber Fabry-Perot interferometer for vibration displacement measurements
Author(s): H C Seat; E Ouisse; V. Metivier; E. Morteau
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Paper Abstract

An extrinsic fibre Fabry-Pérot interferometric (EFFPI) sensor has been successfully demonstrated for the measurement of displacement and/or velocity of a vibrating target. The target employed consists of a combination ofa strip ofretro-reflective microprisms and a linear polariser. It is then bolted onto an oscillating piezo-electric transducer (PZT). Hence, two dissimilarly polarised lightwaves of similar frequency are reflected from each ofthe two surfaces and interfere with light reflected from the end ofthe "sensing" fibre arm, resulting in a double cavity within the arm ofthe interferometer. This provides a relatively simple and practical technique of determining the direction or sense of vibration of the target. The sensing system was found to be relatively immune to minor perturbations, such as small temperature changes (~±5 °C), since the two sets of interference signals propagate along the same optical path. Further, the evolution of the sensor for velocity measurements with angular inclination of the target has been found to agree well with predicted values while changes in velocities measured by the EFFPI sensor with frequency variation of the target at 0° incidence was found to contain slight discrepancies compared to those from the PZT. Typical PZT frequencies investigated ranged from ~14 — 136 Hz. Polarisation effects on the reflected beam from the retro-reflective microprisms have been observed and induced birefringence in the sensing arm due to bends and twists has been attributed as the main reason for measurement errors. The potential resolution attainable from the EFFPI sensor is predicted at better than ?8.

Paper Details

Date Published: 22 May 2002
PDF: 9 pages
Proc. SPIE 4827, Fifth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, (22 May 2002); doi: 10.1117/12.468193
Show Author Affiliations
H C Seat, Ecole des Mines de Nantes (France)
E Ouisse, Ecole des Mines de Nantes (France)
V. Metivier, Ecole des Mines de Nantes (United States)
E. Morteau, Ecole des Mines de Nantes (France)

Published in SPIE Proceedings Vol. 4827:
Fifth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications
Enrico Primo Tomasini, Editor(s)

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