Highly Sensitive Balloon-Like Temperature Fiber Sensor Based on a Seven-Core Fiber

A high sensitivity fiber sensor constructed by cascading a seven-core fiber (SCF) with a balloon-like bending single-mode fiber (BSF) is proposed and demonstrated. Due to the composite structure, more higher-order modes can be stimulated from the core mode than the conventional BSF, leading to a high temperature sensitivity of the sensor. Experimental results show that when the temperature varies from 31 °C to 70 °C, the maximum temperature sensitivity of the sensor can reach −3.22 nm/°C, which is the highest as far as the BSF sensor is concerned. By decreasing SCF’s length and BSF’s diameter, the temperature sensitivity of the sensor will be increased. Furthermore, the sensor is insensitive to the change of the refractive index (RI), which successfully avoids the problem of cross-sensitivity in practical applications of temperature and RI detection.