Biaxial optical fiber sensor based in two multiplexed Bragg gratings for simultaneous shear stress and vertical pressure monitoring

C. Tavares, M. Domingues, A. Frizera-Neto, C. Leitaõ, N. Alberto, C. Marques, A. Radwan, E. Rocon, P. André, P. Antunes

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations


This work consists on the design and implementation of a compact and accurate biaxial optical fiber sensor (OFS) based on two in-line fiber Bragg gratings (FBGs) for the simultaneous measurement of shear and vertical forces. The two FBGs were inscribed in the same optical fiber and placed individually in two adjacent cavities. In the calibration and performance tests, the response from the optical fiber cells was compared with the values given by a three-axial electronic force sensor. Sensitivity values obtained for the FBG1 are K1V= (14.15±0.10) pm/N (vertical force) and K1S= (-26.02±0.08) pm/N (shear force) and for the FBG2 are K2V= (7.35±0.02) pm/N and K2S= (-24.29±0.08) pm/N. The conversion of the Bragg wavelength shift, given by the optical fiber sensors, into the shear and vertical force values is also presented along with its comparison to the values retrieved by an electronic sensor, yielding to low RMSE values, which shows the high accuracy of the algorithm applied. This work stands out from the others with optical fiber by the simplicity of its structure. The proposed solution represents a compact and reliable device for simultaneous measurement of shear and vertical forces, useful in several areas, such as: Incorporation into insoles for plantar pressure and shear force measurement; electronic skin technologies; smart rehabilitation robotic exoskeletons; or even biomimetic prosthesis.

Original languageBritish English
Title of host publicationOptical Sensing and Detection V
EditorsFrancis Berghmans, Anna G. Mignani
ISBN (Electronic)9781510618862
StatePublished - 2018
EventOptical Sensing and Detection V 2018 - Strasbourg, France
Duration: 23 Apr 201826 Apr 2018

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceOptical Sensing and Detection V 2018


  • biaxial optical fiber sensor
  • fiber Bragg grating
  • shear force sensor
  • vertical force sensor


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