In-line fiber Mach-Zehnder interferometers have become more popular than traditional electric sensors because of their small size, low cost, easy fabrication, resistance to electromagnetic interference, durability against extreme environments, and ease of use. This paper discusses the development, characteristics, and properties of a curvature-based Mach-Zehnder interferometer (MZI). The MZI comprises a filter made by splicing core-offset sections of a special mode fiber (SSMF) with a cladding diameter of 70 μm in an SMF-SSMF-SMF-SSMF-SMF (1m/25mm/30mm/25mm/1m) configuration. The SSMF splices act as the arms of the MZI, while the mismatch diameter sections serve as optical fiber couplers. The MZI was characterized by measuring the optical spectrum response when a broadband source of 1537.5 to 1600 nm was launched with a power of 10 dBm to transmit light through the arrangement. The optical spectrum analyzer (OSA) detects the transmitted light and analyzes its optical transmission characteristics, showing 5 notches of modal interferences into the longitude region. As a result of the experimental arrangement, the displacement and curvature sensitivities are 0.003 nm/μm and 0.509 nm/μm-1, respectively. The proposed sensor has potential advantages for measuring refractive index, pH, torsion, curvature, and temperature.
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