An inline Mach-Zehnder interferometer for simultaneously measuring liquid level and temperature

Abstract

A compact optical fiber sensor (OFS) based on an inline Mach-Zehnder interferometer for simultaneousmeasurement of liquid level and the temperature isproposedanddemonstrated experimentally. The proposed sensor is formed by fusion splicing a thin core fiber (TCF) with an ultra-thin fiber (UTF) with core offset, then TCF and UTF are sandwiched between two standards of single mode fibers (SMFs). The liquid level or temperature change will lead to the dips shifts in the interference spectrum, and the liquid level and temperature sensitivities can be measured independently by monitoring the resonance dips shifts. Then the simultaneous measurement of liquid level and temperature can be obtained through the demodulation matrix. Four sensors with different UTF length are fabricated based on numerical simulation. The experimental results show that the proposed sensor with a UTF length of 8 mm has the optimal liquid level and temperature sensitivities of −231.67 pm/mm and 77.86 pm/°C, respectively. The measuring liquid level and temperature ranges are 0–8 mm and 30–60 °C. The proposed sensing configuration has practical application potential in various industries due to the advantages of high sensitivity, simple fabrication and low cost.