Sensitivity Enhancement of a Semicircular Curved Hetero-Core Optical Fiber Accelerometer With Low Cross-Axis Sensitivity

In this article, the frequency, amplitude, and cross-axis sensitivity characteristics of a hetero-core fiber optic accelerometer subjected to mechanical vibrations are presented. The proposed accelerometer is based on a fixed-support structure and can be used for structural health monitoring. It consists of a semicircular curved hetero-core optical fiber with both ends fixed to a base, which operates as a vibration detector. To increase its sensitivity and reduce its cross-axis sensitivity, a hetero-core portion is placed near one of the fixed ends. By fabricating an ideal semicircular beam-shaped acceleration sensor with both ends fixed, good agreement between the experimentally obtained spectrum results and finite element analysis results when the accelerometer is subjected to mechanical vibrations is observed. The accelerometer’s sensitivity is clearly stable at frequencies less than approximately a quarter of the first natural frequencies of 1810, 850, and 350 Hz with sensitivities of 1.45
$\times 10^{-3}$
, 2.80
$\times 10^{-3}$
, and 6.16
$\times 10^{-3}$
dB/g for fiber curvature radii of 7, 10, and 15 mm, respectively. Owing to its highly linear acceleration characteristics, it is possible to efficiently convert the acceleration to optical loss. The cross-axis sensitivity is in the range 4.27%–15.9%, which is better than that of previously reported accelerometer structures, which use a hetero-core fiber sensor located at the center between the two fixed ends without a free supporting point. Therefore, the proposed accelerometer, which consists only of a semicircular-shaped optical fiber, is capable of improving the sensitivity and reducing the cross-axis sensitivity by adjusting the placement of the hetero-core fiber sensor.