TITLE:
Optical Fiber Torsion Sensor with Mechanically Induced Long Period Fiber Gratings in Rare-Earth Doped Fibers
AUTHORS:
Maria Pulido-Navarro, José Álvarez-Chávez, Daniel Ceballos-Herrera, Ponciano Escamilla-Ambrosio
KEYWORDS:
Optical Fiber Sensors, Fiber Bragg Gratingsensors, Torsion Sensors, Rare-Earth Doped Fibers
JOURNAL NAME:
Optics and Photonics Journal,
Vol.4 No.6,
June
20,
2014
ABSTRACT: In this
work wavelength sensitivity in mechanically induced long period fiber gratings
(MLPFG) is analyzed. This analysis is first carried out both in standard single-mode
fiber SMF-28 and in Er-doped fibers. The mechanical analysis for both types of
fibers under different torsion conditions is presented. In order to apply the
torsion one of the fiber ends is fixed while torsion is applied on the other
end. A MLPFG whose period is 503 μm is used to press the fiber after torsion is
applied. This allows for micro curvatures to be formed on the fiber, which in
turn generates a periodical index perturbation on it. Here, it was noted that
the sensitive wavelength shift of the rejection bands is bigger for Er-doped
fibers. For a torsion of 6 turns applied to 10 cm of doped fiber the wavelength
peaks can be moved up to 25 nm, which is longer to what was detected on
standard fibers. Therefore, by using Er-doped fibers to monitor torsion on
structures will give more sensitive and accurate results than using standard
fibers. These results can be employed for sensing applications, especially for
small to medium size structures, which can be mechanical, civil or aeronautics.