High-sensitivity strain sensor based on two different specialty fibers and the Vernier effect

What we believe to be a novel strain sensor based on a three-core fiber (3MCF-V) and the Vernier effect was developed and characterized, offering a wide strain measurement range and temperature compensation. The sensor combined a Fabry-Perot interferometer (FPI) formed by a hollow-core fiber (HCF) and a super-modes interferometer (SMI) using a multicore fiber (MCF). By combining these two interferometers in a parallel Michelson configuration, a Vernier envelope amplified the response of the system, achieving higher strain sensitivity compared to conventional approaches. The sensor demonstrated a linear response, with a sensitivity of 5 pm/µε for a 30 mm fiber segment, out of the 230 mm that make up the SMI, and up to 22.2 pm/µε when the length of the segment under deformation was increased to 85 mm, reaching a deformation of up to 6280 µε without causing the fiber to break. Additionally, a thermal analysis validated a temperature sensitivity of 766.5 pm/°C, confirming the robustness and accuracy of the proposed design. These results highlight the potential of the sensor for advanced strain or temperature monitoring applications requiring high resolution over a broad dynamic range.