Refractive index and temperature sensor based on no-core fiber and few-mode fiber coupling

An interferometric fiber optic sensor based on no-core fiber (NCF) is proposed, and small sections of few-mode fiber (FMF) are fused to each end of the NCF to enhance the sensitivities of the sensor. The refractive index sensitivities of this structure are 171.29 nm/RIU from 1.35 to 1.41 and 892.56 nm/RIU from 1.41 to 1.43, respectively. The temperature sensitivity is 0.06684 nm/°C from 30°C to 90°C. The proposed sensor has the advantages of simple structure, low cost and anti-electromagnetic interference, which can be widely used in biological and chemical fields.