Multi-parameter optical fiber sensor based on enhanced multimode interference

In this paper, a multi-parameter optical fiber sensor based on all-fiber in-line single-mode-multimode-no-core-single-mode (SMNS) structure is proposed and experimentally demonstrated. A section of multimode fiber (MMF) is utilized as the mode coupler to enhance the multimode interference (MMI). A 58.5 mm long no-core fiber (NCF) acts as the sensing head, which is modified by the surrounding medium. The experimental results exhibit that the sensor possesses a water level sensitivity of 215.98 pm/mm by monitoring the wavelength shift at 1586.03 nm, and −0.11 dB/mm of the power attenuation at the wavelength of 1600.05 nm with a measurement range of 58.33 mm. At the same time, the RI sensitivities of 131.71 nm/RIU and the axial strain sensitivity of −1.21 pm/µε are also obtained.