High-sensitivity fiber temperature and refractive index sensing with nonadiabatic fiber taper
In the paper, simultaneous measurement temperature and external refractive index is achieved in the present scheme, this scheme is based on Mach-Zehnder interferometer using a nonadiabatic single mode fiber taper without an air cavity. This scheme is quite simple and the smallest diameter of the tapered fiber is about 83.1 micrometers and the length of tapered fiber is about 1 centimeter. The transmission spectrum of the nonadiabatic tapered fiber exhibits a number of resonance wavelength dips which corresponds to different orders of cladding modes. The interferometer can be used for simultaneous refractive index (RI) and temperature sensing by monitoring the variation of selected two wavelength dips. The sensitivity achieved are -44.69 nm/RIU and 0.0386 nm/C, and -72.21 nm/RIU and 0.0321 nm/C for refractive index (RI) and temperature, respectively. The proposed tapered single mode optical fiber interferometer would find potential applications in multiple-parameter sensing owing to its high sensitivity, compactness, ease of fabrication, and low cost.