In-Line Mach–Zehnder Interferometric Sensor Based on a Linear Five-Core Fiber

A linear five-core fiber was sandwiched in between two single-mode fibers to construct an all-fiber Mach-Zehnder interferometer (MZI). The linear five-core fiber can support multiple supermodes due to a small distance between two adjacent cores. The interferences between the fundamental supermodes, between the fundamental supermodes and the high-order core modes, and between the fundamental supermodes and the low-order cladding modes are investigated. The proposed MZI can realize strain, temperature, and curvature fiber sensors. The experimental results show both the interference between the core modes and the interference between the core modes and the cladding modes have approximately equal temperature sensitivity. The interference between the core modes is insensitive to the axial strain and the bending. In contrast, the interference between the core and the cladding modes is highly sensitive to the strain and the bending perpendicular to the arranged plane of the cores, the corresponding strain and bending sensitivities are 0.8 pm/με and 10.37 nm/m^-1.