Helicity Enhanced Torsion Sensor Based on Liquid Filled Twisted Photonic Crystal Fibers

• Main Authors: Feng Zhang, Ying Wang, Zhiyong Bai, Shen Liu, Cailing Fu, Yijian Huang, Changrui Liao, Yiping Wang
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Sensors
• Subjects: fiber optics sensors; photonic crystal fibers; microstructure fabrication
• Online Access: https://www.mdpi.com/1424-8220/20/5/1490

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, <i>&#945;</i>₀) of the twisted photonic crystal fiber. The enhancement mechanism of <i>&#945;</i>₀ 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^&#8722;1 can be obtained by tailoring these parameters. Experimental results show that the torsion sensitivity increases with <i>&#945;</i>₀ 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.