High-temperature sensor based on a special thin-diameter fiber

Abstract

We proposed and experimentally demonstrated a novel compact high temperature sensor, based on a special thin-diameter fiber (TDF) sandwiched between two segments multimode fibers (MMFs). The TDF is specially designed with 20μm cladding radius and 3.5μm core radius, which is pliable to fabricate a robust all fiber high temperature Mach–Zehnder interferometer (MZI). The clear interference spectrums of TDF-MZI structures with TDF length at 5 mm, 10 mm and 27 mm, are obtained in our experiments and analyzed in spatial frequency domain. The transmission characteristics of the light propagating in the TDF based MZI structure, with the MMFs connected or not, are researched and compared in experiments and theoretical simulations. A theoretical comparative study on the fiber thermal expansion between 40μm fiber and 125μm fiber is given, under the temperatures varying from 100 °C to 1000 °C, and the simulation results show that the TDF-MZI suffers a relatively larger thermal stress than that of the normal diameter fiber (typically 125μm). Experimental results also demonstrated that the TDF-MZI has a relatively high temperature sensitivity of 0.088 nm/°C, 0.150 nm/°C and 0.285 nm/°C, in the range of 100–650 °C, 650–850 °C and 900–1000 °C, respectively. The TDF-MZI device is straightforwardly fabricated by only fiber fusion splicing, which make it simple, reproducible and low cost, and have potential for practical applications in various industrial processes