Optical Fourier Domain Reflectometry enables to measure strain gradients and temperature changes underneath the surface by using optical fibers. The status of an optic–electric composite high-voltage submarine cable (referred to as submarine cable) can be monitored based on optical fiber-distributed sensing technology, and at the same time, no additional sensor is needed in the monitoring system. Consequently, damages and strains within fiber-reinforced composites can be unveiled. Unlike traditional straingauges, fiber-optic measurement processes. Addressing unclear strain transfer and underdeveloped Brillouin optical time-domain reflectometry (BOTDR) sensing models for three-core fiber-optic composite submarine cables, this study investigated a 66 kV cable and clarified a BOTDR monitoring principle based on the three-layer mechanical.
