Temperature-insensitive strain sensor based on few-mode fiber

• Published in: Optical fiber technology Vol. 73; p. 103034
• Main Authors: Gao, Xuekai, Xu, Jian, Zhang, Wei, Lei, Feipeng, Zheng, Jingjing, Pei, Li, Wang, Jianshuai, Chai, Jinchuan, Ning, Tigang
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.2022
• Subjects: Few-mode fiber; Fiber optical sensor; Strain; Fiber optical sensor; Few-mode fiber; Strain
• ISSN: 1068-5200; 1095-9912
• DOI: 10.1016/j.yofte.2022.103034

•Simple structure with relative high strain sensitivity and low temperature sensitivity.•The proposed sensor solves the problem of cross-sensitivity to a certain extent.•The duplicate sensor keeps the same strain and temperature characteristics that suggests excellent fabrication repeatability of the proposed sensor.•We study the relationship between amplitude variation and temperature variation to obtain the indicators of strain sensitivity. An all-fiber strain sensor based on the few-mode fiber (FMF) hybrid construction is proposed and experimentally demonstrated to solve the problem of cross-sensitivity between strain and temperature. The proposed sensor is constructed by three pieces of FMFs that are the dislocation fusion structure. The strain sensitivity of the sensor is analyzed by the wavelength shift and light intensity. According to the wavelength shift analysis, experimental results show that the strain sensitivity of the proposed sensor is −3.13 pm/με and −2.85 pm/με at the wavelength of resonance peaks dipA and dipB in the strain range from 0 to 700 με. Meanwhile, the wavelengths of resonance peaks dipA and dipB show few wavelengths shift in the temperature range of 20–60 °C, which provides the possibility for the proposed sensor in strain sensing applications without cross-sensitivity under a temperature range of 20–60 °C. According to the light intensity analysis, we find that there is a linear relationship between the amplitude of the spatial frequency spectrum and strain variation, and the amplitude decreases with the increase of strain at 0.026 nm−1 and 0.045 nm−1. The strain sensitivity is −0.0003 a.u./με at 0.026 nm−1 and −0.0004 a.u./με at 0.045 nm−1, and there is no spatial frequency shift as the strain increases. Very importantly, the duplicate sensor keeps the same strain and temperature characteristics that suggests excellent fabrication repeatability of the proposed sensor. From the aspects of practicality and performance, the proposed strain sensor is not only easy to construct but also temperature insensitive. These advantages make the proposed strain sensor very promising in practical sensing applications under different temperatures.