High Sensitivity Balloon-Like Sensor Based on Twin-Core and Twin-Hole Fiber

An all-fiber Mach–Zehnder interferometric (MZI) sensor for measuring temperature and refractive index (RI) is proposed and experimentally demonstrated. A high sensitivity balloon-like mode interferometer is fabricated with a twin-core and twin-hole fiber (TCTHF). The variations in ambient temperature and RI cause changes in phase differences between the modes, leading to shifts in the interference spectrum. The two resonance dip wavelength shifts within the spectrum are used to investigate the temperature and RI characteristics of the sensor. Experimental results show that the two dips have different responses to temperature and RI, indicating that the sensor can realize simultaneous measurement of temperature and RI. The obtained maximum sensing sensitivities are 0.051 nm/°C and 423.168 nm/RIU. The proposed sensor has potential applications in physical, biological, and chemical sensing owing to its high sensitivity, low cost, and small size.