Strain Transfer Effect in Distributed Fiber Optic Sensors under an Arbitrary Field

Optical fibers with protective coatings have been used as distributed strain sensors for automated inspection in the construction, operation, and maintenance of various engineering structures. The presence of the protective coatings causes strain transfer effect, which can change the strain measurement of the distributed sensors. This study quantitatively evaluates the strain transfer for distributed fiber optic sensors subjected to an arbitrary strain field for the first time. Theoretical studies are performed to derive closed-form solutions for describing the strain transfer, and high-resolution (sub-millimeter) strain distributions were measured to validate the theoretical study. This study demonstrates that the strain transfer effect is dependent on the strain field in the host matrix, and the derived formulae enable correct interpretation of the strain measurement from the distributed sensor. This study provides theoretical foundations for using distributed fiber optic sensors to accurately measure strain distributions in engineering structures