Curvature and Vibration Sensing Based on Core Diameter Mismatch Structures

• Published in: IEEE transactions on instrumentation and measurement Vol. 65; no. 9; pp. 2120 - 2128
• Main Authors: Fernandes, Cindy S., Rocco Giraldi, Maria Thereza M., de Sousa, Marco J., Costa, Joao C. W. A., Gouveia, Carlos, Jorge, Pedro, Franco, Marcos A. R.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-09-2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bragg gratings; Core diameter mismatch (CDM); Curvature; Detection; Mathematical analysis; Optical attenuators; optical curvature sensor; Optical device fabrication; Optical fibers; Optical interferometry; Optical sensors; Optical variables measurement; optical vibration sensor; Sensors; single-mode–multimode–single-mode (SMS); SMSMS; Splicing; Vibration; Vibrations; Wave attenuation
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2016.2571378

Core diameter mismatch structures are proposed and experimentally investigated for curvature and vibration sensing. Two configurations are suggested, one approach uses a structure formed by splicing an uncoated short section of multimode fiber between two standard single-mode fibers (SMFs) single-mode-multimode-single-mode (SMS), combined to a fiber optical mirror at its end, and the other approach uses a structure made by splicing a section of SMF between two multimode fibers (SMSMS). In the curvature analysis, the proposed SMS sensor generates the destructive interference patterns when it is bent, varying only the attenuation of the optical signal without wavelength shifts. The SMSMS vibration sensor proved to be suitable to monitor very low frequencies such as 0.1 Hz. The configuration of the proposed sensors presents several interesting features, such as easy fabrication, low cost, high efficiency, and high sensitivity. These advantages make such sensors very useful in a wide range of applications, for instance, structural health monitoring.