Abstract

We demonstrated a novel long-period fiber grating (LPFG) written in a tri-hole fiber (THF). The LPFG was fabricated by periodically collapsed micro holes utilizing CO₂ laser irradiation integrated with pressure-assisted technology. The mode coupling between the fundamental mode and higher mode of the proposed grating is mainly caused by geometric deformation along the fiber axis. Compared with conventional LPFGs, such a grating has strong refractive index modulation due to periodic collapsed structure. We have established an approximate hypothesis to simulate the transmission spectrum of the grating. The measured spectrum is basically consistent with the simulated transmission spectrum at the resonant peak position. We investigated the sensing characteristics of the proposed LPFG, including axial strain, bending, torsion, and temperature. The sensitivity of bending, temperature and torsion are −9.56 nm/m⁻¹, 162.8 pm/(rad/m) in clockwise and −346.9 pm/(rad/m) in counterclockwise and 86.8 pm/°C, respectively. The experimental data shows that the fabricated LPFG has potential applications in the field of external high-sensitivity strain sensing with a sensitivity of −26 pm/με.

Photonic crystal fiber interferometer composed of a long period fiber grating and one point collapsing of air holes

Hae Young Choi, Kwan Seob Park, and Byeong Ha Lee
Opt. Lett. 33(8) 812-814 (2008)

Bending characteristics of a long-period fiber grating in a hollow eccentric optical fiber

Xing Zhong, Chunying Guan, Guopei Mao, Jianan Fu, Yang Liu, Jinhui Shi, and Libo Yuan
Appl. Opt. 54(26) 7879-7883 (2015)

Residual-stress-induced helical long period fiber gratings for sensing applications

Ziliang Li, Shen Liu, Zhiyong Bai, Cailing Fu, Yan Zhang, Zhongyuan Sun, Xueya Liu, and Yiping Wang
Opt. Express 26(18) 24114-24123 (2018)

Long period fiber grating based on periodically screw-type distortions for torsion sensing

Mi Deng, Jinshan Xu, Zhe Zhang, Zhiyong Bai, Shen Liu, Ying Wang, Yan Zhang, Changrui Liao, Wei Jin, Gangding Peng, and Yiping Wang
Opt. Express 25(13) 14308-14316 (2017)

Characteristics of chiral long-period fiber gratings written in the twisted two-mode fiber by CO₂ laser

Xibiao Cao, Yunqi Liu, Liang Zhang, Yunhe Zhao, and Tingyun Wang
Appl. Opt. 56(18) 5167-5171 (2017)