RI and temperature sensing based on cascaded core-offset structure with thin-core fiber

According to the theory of inter-mode interference, an interferometer based on cascaded core-offset structure with thincore fiber (TCF) is researched. The core-offset structure acts as a coupler, allowing energy to enter the cladding of the fiber, thereby exciting the cladding modes. The interference occurs twice in the proposed interferometer. The first time occurs at the joint of the single-mode fiber (SMF) 2 and TCF, and the second time occurs at the joint of the TCF and the SMF3. Both the temperature and refractive index (RI) sensing experiment are conducted. The maximum temperature and RI sensitivity are -161nm/RIU and 0.069nm/°C, respectively. The studied sensors have good characteristics such as simple manufacturing, low cost and high mechanical strength. So the sensor has the potential to be applied in practice.