Abstract
We proposed and demonstrated a compact inline optical fiber sensor for curvature and temperature measurement with low cross sensitivity. The device consists of a 5 mm long hollow-core fiber (HCF) spliced between two single-mode fibers. Two up-tapers were fabricated at each splicing joint forming a Mach-Zehnder Interferometer (MZI). The HCF acted as the anti-resonant reflecting optical waveguide (ARROW), giving periodic dips at resonant wavelengths in the optical transmission spectrum. The cross sensitivity of curvature and temperature problem is solved by demodulating the wavelength shift of the MZI for temperature sensing and intensity variation of ARROW dips for curvature sensing. The curvature and temperature sensitivities are experimentally measured to be -4.28 dB/m -1 and 25.76 pm/°C, respectively. The cross sensitivities for ARROW is measured to be 0.0056 m -1 /°C. The structure of the sensor is simple and compact, which can be used for structural health monitoring in a complex environment.
Highlights
Optical fiber sensors have been extensively studied due to their intrinsic advantages of light weight, small size, flexibility, and immunity to electromagnetic interference
We proposed and demonstrated a compact inline optical fiber sensor for curvature and temperature measurement with low cross sensitivity
The hollow-core fiber (HCF) acted as the anti-resonant reflecting optical waveguide (ARROW), giving periodic dips at resonant wavelengths in the optical transmission spectrum
Summary
Optical fiber sensors have been extensively studied due to their intrinsic advantages of light weight, small size, flexibility, and immunity to electromagnetic interference. The MZI is usually formed by splitting and later recombining different optical modes, i.e., core mode and cladding modes, at two separate fiber mode-coupling joints. The mode-coupling joints can be produced by fiber taper [4], [9], [14], dual-core fiber [15], lateral-offset splicing [16], or photonic crystal fiber collapsing [12] Among these techniques, fiber taper is a favorable option because of its low cost and ease of operation with high reproducibility. We reported a curvature sensor based on anti-resonant reflecting optical guidance (ARROW) [13]. Since we are monitoring two different aspects of the transmission spectrum, i.e., wavelength shift and dip intensity, the temperature and curvature cross-sensitivity can be largely eliminated through this demodulation technique
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