Strain measurement using fiber-optic sensors: a review

Abstract

The paper presents a review of research related to strain measurement using fiber-optic sensors (FOS). Single-point FOS based on fiber Bragg gratings and distributed FOS based on Rayleigh scattering are considered. A brief history of FOS development is presented, along with an overview of basic operating principles of point and distributed sensors. Applications of FOS in aircraft structures, geotechnical monitoring, civil infrastructure, medicine, and biomechanics are discussed. Particular attention is paid to factors that determine the reliability of strain values measured by point and distributed FOS: strain transfer from the measured object to the optical fiber region where measurements are performed; changes in the structure and stress-strain state of the material after FOS embedding; accounting for the complex stress state in the optical fiber when calculating strain from physical quantities recorded by the sensor; the influence of temperature and humidity; and the influence of strain gradients. The paper also analyzes the use of FOS embedded in materials to measure process-induced and residual strains in polymer and composite materials manufactured via various chemical molding and additive manufacturing technologies. It is shown that correct interpretation of sensor readings requires consideration of the physical principles of measurement, bonding or embedding conditions, material properties, and data processing algorithms. Promising areas for the application of FOS are considered.