Research on a strained sensing optical cable based on rectangular structure and weak fiber Bragg grating array

Abstract In the strain monitoring of high-traffic infrastructure, there is a growing demand for a strained sensing optical cable that provide high adaptability and accuracy without invasive installation. A rectangular structure optical fiber sensing cable based on weak fiber Bragg grating (wFBG) is proposed to satisfy these requirements in this research. The cable features a multilayer composite structure, consisting of an optical fiber inscribed with a dense array of wFBG and an outer protective layer made of either linear low-density polyethylene (LLDPE) or thermoplastic polyurethane. The rectangular geometry is designed to maximize surface contact, and thereby facilitate surface mounting. Two gluing methods are investigated, namely bonding with a carbon-fiber-reinforced polymer (CFRP) resin layer and fixation using 3 M™ double-sided adhesive tape. A theoretical strain transfer model is established to analyze the sensing performance, and experimental validation is conducted through a simply supported beam load test and hysteresis loop measurements. These results demonstrate that the LLDPE&CFRP configuration achieves the highest strain transfer efficiency of approximately 92.6%, with measurement errors below 3%. This configuration also exhibits the smallest hysteresis loop area, indicating superior elastic recovery and stable strain coupling. These characteristics highlight the potential of the proposed design as a reliable and high-performance solution for strain monitoring under complex installation and service conditions.