Mach-Zehnder interferometer for multi-parameter measurement sensor based on SMF-NCF-FMF-NCF-SMF

A Mach-Zehnder interferometer sensor is designed, which includes a cascade structure of single-mode fiber (SMF)-no-core fiber (NCF)-few-mode fiber (FMF)-no-core fiber (NCF)- single-mode fiber (SMF) (SNFNS). In this structure, the NCF is used as the input and output coupler, and the FMF is used as the sensing region. In the measurement range, the SNFNS sensor has three interference dips. Among them, temperature and humidity can be measured simultaneously through the dip2 and the dip3, temperature and refractive index can be measured simultaneously by the dip1 and dip2. The temperature sensitivities are 0.063 nm/℃, 0.013 nm/℃ and 0.095 nm/℃ in the range of 30 ℃~85 ℃. When refractive index changes from 1.333 to 1.365, the refractive index sensitivities of the dip1 and the dip2 are 134.17 nm/RIU and 53.76 nm/RIU, respectively, the changes of the dip3 are not noticeable. When humidity changes from 30%RH to 70%RH, the humidity sensitivities of the dip2 and dip3 are 0.034 nm/%RH and 0.025 nm/%RH, respectively, the changes of the dip1 are not noticeable. Furthermore, the structure has the merits of simple construction, good repeatability, and good stability.