Light transmission mechanisms in a SMF-capillary fiber-SMF structure and its application to bi-directional liquid level measurement

Huang, Ziyi, Liu, Dejun, Wu, Qiang, Tian, Ke, Zhao, Haoyu, Shen, Changyu, Farrell, Gerald, Semenova, Yuliya and Wang, Pengfei (2022) Light transmission mechanisms in a SMF-capillary fiber-SMF structure and its application to bi-directional liquid level measurement. Optics Express, 30 (12). pp. 21876-21893. ISSN 1094-4087

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Capillary fiber (CF) has been extensively investigated in a singlemode fiber (SMF)CF-SMF (SCS) sensing structure since multiple light guiding mechanisms can be easily excited by simply tuning the air core diameter (cladding diameter) and length of the CF. Understanding the light guiding principles in an SCS structure is essential for improved implementation of a CF based fiber sensor. In this work, light guiding principles in a relatively large air core diameter (≥ 20 µm) and long length of CF (> 1 mm) are investigated theoretically and experimentally. It is found that both multimode interference (MMI) and Anti-Resonant Reflecting Optical Waveguide (ARROW) light guiding mechanisms are excited in the SCS structure in the transmission configuration. However, MMI dips are not observed in the spectrum for the air core diameters of CF smaller than 50 µm in the experiment due to large transmission loss in small air core CFs. Further experimental results demonstrate that a CF with a bigger air core diameter shows a higher sensitivity to curvature, and the highest sensitivity of -16.15 nm/m−1 is achieved when an CF-100 was used. In addition, a SMF-CF-20-CF-30-SMF (SCCS) structure is proposed for high sensitivity bi-direction liquid level measurement for the first time, to the best of our knowledge. Two types of ARROW dips (Dip-20 and Dip-30) are simultaneously excited in transmission, hence both liquid level and liquid flow direction can be detected by tracing the dip strength changes of Dip-20 and Dip-30, respectively.

Item Type: Article
Additional Information: Funding Information: Funding. National Natural Science Foundation of China (11874332, 62105217); Basic and Applied Basic Research Foundation of Guangdong Province (2019A1515110320); Shenzhen Fundamental Research Program (JCYJ20190808140805488, JCYJ20190808173401660, JCYJ20190808173619062); National Key Scientific Instrument and Equipment Development Projects of China (61727816). Open Access information:
Subjects: F300 Physics
H600 Electronic and Electrical Engineering
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Rachel Branson
Date Deposited: 27 Jul 2022 14:25
Last Modified: 27 Jul 2022 14:30

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