Strain Transfer Model Assessment for Steel-Reinforced and Polymer-Coated Optical Fiber Cables Used as Distributed Strain Sensors

Strain transfer in distributed optical fiber sensors is typically represented by a simplified 1-D model that incorporates a strain lag parameter dependent on cable characteristics and installation conditions. Initially developed for thin cables with polymer coatings, this study extends the evaluation of the model's applicability to robust four-layered cables—one with polymer coatings only and the other including a steel layer—designed for use in harsh environments and complex installation scenarios. Finite element simulations are conducted to assess the model's performance for both steel-reinforced and polymer-coated cables subjected to strain gradients, using strain lag parameters specific to each cable. The results demonstrate that the model accurately predicts strain transfer in steel-reinforced cables but shows reduced accuracy for polymer-coated cables. Furthermore, the influence of the precision of the strain lag parameter and variations in interlayer stiffness, governing the interfacial behavior and affected by installation practices, on the model's validity is critically examined.