Multipoint real-time displacement sensing method employing multi-wavelength by intensity-based hetero-core fiber optics sensors

Abstract

The intensity-based measurement could be necessary to smart structures embedding multipoint fiber optic sensors for real-time monitoring such as the human motion in daily activity. Hetero-core fiber optic displacement sensor has great advantage to the intensity-based measurement because the sensitivities of hetero-core fiber optic displacement sensors change by different of the hetero-core insertion length and the transmission wavelength. This paper proposed the new approach for multipoint real-time measurement of hetero-core fiber optic intensity-based sensors. The bending optical loss characteristics of hetero-core fiber optic sensor were measured about four kinds of hetero-core insertion lengths at the two wavelengths, 0.85 μm and 1.31 μm. The bending displacement of two sensors on a single transmission line could be successfully detected by using two hetero-core fiber optic sensors to have the different hetero-core insertion lengths at the two wavelengths of 0.85 μm and 1.31 μm. The accuracies of two sensors, which had the hetero-core insertion lengths of 0.5 and 1.0 mm, with tandem connection were ±0.003 mm and ±0.003 mm of the displacement, ±2.87 % and ±0.63 % for the full-scale displacement of 2 and 0.5 mm, respectively.