All-Fiber Liquid-Level Sensor Based on In-Line MSM Fiber Structure


We propose and demonstrate an all-fiber liquid-level sensor using an in-line multimode-single-mode-multimode (MSM) fiber structure. A piece of single-mode fiber (SMF) is spliced to two sections of equivalent multimode fiber (MMF) which are used as both mode splitter and mode coupler. The cladding mode will be excited when the light propagates from MMF to SMF, and then it will be combined with fundamental mode to form a Mach-Zehnder interferometer (MZI) when the light propagates from SMF to the other MMF. The liquid level is detected by the selected resonant dips shift of the transmission spectrum. A sensing sensitivity of 264.6 pm/mm is achieved for the proposed sensor with an SMF length of 26mm. Due to its compact structure, easy fabrication, and high sensitivity, the proposed liquid-level sensor is attractive for practical applications in a variety of fields, such as marine detection and chemical processing.


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This study was supported in part by the National Natural Science Foundation of China (NSFC) (Grant Nos. 61727816, 61520106013, and 61705031), in part by China Postdoctoral Science Foundation (Grant Nos. 2017M610175 and 2018T110216), in part by Fundamental Research Funds for Central Universities (Grant No. DUT19LAB32) Sponsor, and financial support acknowledgments are placed here.

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Correspondence to Wei Peng.

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Sun, T., Liu, Z., Liu, Y. et al. All-Fiber Liquid-Level Sensor Based on In-Line MSM Fiber Structure. Photonic Sens (2020).

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  • Liquid-level sensor
  • MSM fiber structure
  • MZI
  • optical fiber sensor