Abstract
A highly sensitive torsion sensor can be constructed by combining a twisted photonic crystal fiber with a liquid-filled waveguide in its air-hole cladding. The torsion sensitivity of this type of sensor is determined directly by the phase-matching conditions between the fiber core mode and the liquid waveguide mode, which can be improved by tuning the helicity (denoted by the initial twist rate, α0) of the twisted photonic crystal fiber. The enhancement mechanism of α0 on the sensitivity of the proposed torsion sensor is investigated theoretically, followed by experimental verifications, and a torsion sensitivity as high as 446 nm∙mm∙rad−1 can be obtained by tailoring these parameters. Experimental results show that the torsion sensitivity increases with α0 decreasing from 3.142 to 3.925 rad/mm, which are in consistence with that of the numerical predictions. The demonstrated torsion sensor is expected to contribute to the development of highly sensitive torsion-related photonic crystal fiber devices.
Highlights
Torsion measurements based on optical fibers have been applied to many fields including robotics, manufacture industry, and civil engineering
We proposed a series torsion sensors based on twisted photonic crystal fibers with an embedded helical liquid waveguide in the cladding
Because of the directional coupling between the fiber core mode and the liquid waveguide modes, resonant dips appear in the transmission spectrum from 1250 to 1650 nm
Summary
Torsion measurements based on optical fibers have been applied to many fields including robotics, manufacture industry, and civil engineering. PCF (LFTPCF), which presents veryPCF high (LFTPCF), sensitivity and definite direction demonstrated a torsion sensor based on a liquid-filled helical which presents very discrimination for torsion measurement [17]. For the the dispersion curve point of fiberwere core mode is slightly differentin forFigure each α02 curves of proposed liquid rodsensor, and the phase-matching calculated and plotted and is not presented forproposed clarity. 0. It should be noted that to thethe liquid rod supports point a few shifts high-order modes for wavelengths each case of αbecause discuss the corresponds phase-matching toward shorter of the decrease. 3.142 rad/mm can be seen as the inset of Figure 2
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