Abstract

In this paper, the sensing characteristics of a double cladding fiber (DCF) long-period fiber grating (LPFG) to the surrounding refractive index (SRI) are studied. The outer cladding of the DCF plays the role of the overlay, thus, the mode transition (MT) phenomenon of DCF can be induced by etching the outer cladding radius instead of coating overlays. The response characteristics of the effective refractive index (ERI) of the cladding mode to the outer cladding radius are analyzed. It is found that in the MT range, the change rate of ERIs of cladding modes is relatively larger than that for other ranges. Further, based on the features of the mode transition region (MTR), the phase-matching curve of the 11th cladding mode is investigated, and the response of the DCF-LPFG to the SRI is characterized by the change of wavelength intervals between the dual peaks under different outer cladding radii. The numerical simulation results show that the SRI sensitivity is greatly improved, which is available to 3484.0 nm/RIU with the fitting degree 0.998 in the SRI range of 1.33–1.37. The proposed DCF-LPFG can provide new theoretical support for designing the DCF-LPFG refractive index sensor with excellent performances of sensitivity, linearity and structure.

© 2021 Optical Society of Korea

Theoretical analysis of dual-mode long period fiber grating sensor based on dual-peak resonance for dual-parameter measurement

Qiang Ling, Zhengtian Gu, and Tianqi Guan
OSA Continuum 4(3) 1041-1048 (2021)

Characteristics of dual-peak resonance in a tilted long-period fiber grating sensing film sensor

Jiangang Sang, Zhengtian Gu, and Qiang Ling
J. Opt. Soc. Am. B 34(11) 2358-2366 (2017)

Highly sensitive surface plasmon resonance sensor utilizing a long period grating with photosensitive cladding

Zhihong Li, Tao Chen, Zhaogang Zhang, Yanming Zhou, Dan Li, and Zhong Xie
Appl. Opt. 55(6) 1470-1480 (2016)

Mode transition in high refractive index coated long period gratings

A. Cusano, A. Iadicicco, P. Pilla, L. Contessa, S. Campopiano, A. Cutolo, and M. Giordano
Opt. Express 14(1) 19-34 (2006)

Tuning the resonance of polarization-degenerate LP_1,l cladding mode in excessively tilted long period fiber grating for highly sensitive refractive index sensing

Zhihong Li, Jie Shen, Qiuping Ji, Xiukai Ruan, Yaoju Zhang, Yuxing Dai, and Zhennao Cai
J. Opt. Soc. Am. A 35(3) 397-405 (2018)