Optical fiber temperature sensor based on dumbbell-shaped Mach–Zehnder interferometer

A dumbbell-shaped and core-disconnected microstructure all-fiber temperature sensor based on the Mach–Zehnder interferometer (MZI) is designed and implemented. To the best of our knowledge, the MZI with this configuration was produced and applied to sense temperature for the first time. It demonstrated that this all-fiber interferometer incorporates intermodal interference between the LP01 mode and a high-order cladding mode of LP07. Theoretical and experimental results indicate that the linearity of the spectral shift due to the temperature change is ∼0.999 and the sensitivity at 25°C to 400°C is ∼26.03 pm/°C and at −25°C to 20°C is ∼23.87 pm/°C. The reproducibility error of this all-fiber temperature sensor at 25°C to 400°C is <0.71%. Benefiting from the advantages of low cost, compact structure, and environment friendliness, this dumbbell-shaped sensor is expected to be one of the innovative micro–nano all-fiber sensors.