Verification of Optimal Installation Point of FBG Sensor for Pulsation Strain Measurement

This study aimed to identify the optimum installation position of a fiber Bragg grating (FBG) sensor for accurate detection of radial artery pulsation strain. Six FBG sensors were installed in two rows and three columns at 5-mm intervals, and the average wavelength shift length due to pulsation strain was calculated from the six pulsation strain signal waveforms measured simultaneously and analyzed using a
$3\times $
5 matrix. Pulsation strain was detected with a downward or smaller upward strain signal as the measurement point was farther from the pulsation point. Larger strain was detected at the measurement points away from the pulsation point in the arterial or axial directions of the optical fiber than in the oblique direction. At measurement points farther from the pulsation point in the direction of the radial artery, the pulsation strain signal was greater than at measurement points farther in the axial direction of the optical fiber. The pulsation strain signals were measured at a wavelength shift of approximately 50% of the signal measured at the pulsation point at measurement points ±5 mm away in the direction of the radial artery. Therefore, the optimal measurement point of the FBG sensor was found to be within ±5 mm in the arterial direction, including the pulsation point. The results of this study will contribute to the development of textile products (smart textiles) that can measure biological information using FBG sensors.