title: Online fabrication scheme of helical long-period fiber grating for liquid-level sensing.
abstract: We present a novel online fabrication scheme of helical long-period fiber gratings (H-LPFGs) by directly twisting a standard single-mode fiber (SMF) in a microheater. This is done by taking advantage of the inherent core-cladding eccentricity in SMF. We adopt a fiber optic rotary joint to eliminate the accompanying twisting spiral for real-time spectral monitoring and a stepping mechanical system to accurately control the twisting length in fabrication. As a consequence, low-cost and high-quality H-LPFGs can be readily fabricated. Meanwhile, by using this kind of H-LPFG, we design a simple and low-cost wavelength-interrogated liquid-level sensor with a high sensitivity of 0.1 nm/mm.
authors.forename: Kaili
authors.initials: K
authors.lastname: Ren
authors.forename: Liyong
authors.initials: L
authors.lastname: Ren
authors.forename: Jian
authors.initials: J
authors.lastname: Liang
authors.forename: Xudong
authors.initials: X
authors.lastname: Kong
authors.forename: Haijuan
authors.initials: H
authors.lastname: Ju
authors.forename: Yiping
authors.initials: Y
authors.lastname: Xu
authors.forename: Zhaoxin
authors.initials: Z
authors.lastname: Wu