Simultaneous Detection of Liquid Level and Refractive Index with a Long-Period Fiber Grating Based Sensor Device


In this study, a long-period fiber grating (LPFG)-based optical fiber sensor device is proposed for simultaneous detection of liquid level and refractive index (RI). When part of the grating was submerged in an unknown liquid, the resonant wavelength of each cladding mode of the LPFG sensor varied linearly with the submerged length and nonlinearly with the RI of the liquid. By retaining the first-order (sensitivity) and second-order (cross sensitivity) terms of a Taylor expansion of the nonlinear relation, the changes in submerged length (or liquid level) and RI can be simultaneously evaluated from the changes in resonant wavelength of two cladding modes. The sensitivity coefficients to liquid level, RI, their cross effect and environmental effects were studied both analytically and experimentally. The maximum prediction error by the proposed evaluation algorithm was found to be 1 mm for liquid level and 0.005 for RI.


Civil, Architectural and Environmental Engineering

Second Department

Electrical and Computer Engineering

Keywords and Phrases

Multiple Parameter Sensing; Evaluation Algorithm; Liquid Level; Long Period Fiber Grating; Optical Fiber Sensor; Resonant Wavelengths; Sensitivity Coefficient; Simultaneous Detection; Diffraction Gratings; Refractive Index

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


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© 2013 IOP Publishing Ltd., All rights reserved.

Publication Date

01 Sep 2013