Tapered fibre Mach-Zehnder interferometer for simultaneous measurement of liquid level and temperature

A tapered fibre Mach-Zehnder interferometer sensor is presented to simultaneously measure liquid level and temperature. The transmission spectra shift with the change in immersed liquid level and environmental temperature. The liquid level difference of 190 mm can be measured with millimetre resolution in 90 mm-long linear range. The temperature response is discriminated from level response by simultaneously monitoring different interference orders at 1520 and 1620 nm. Level sensitivities of 0.017 and 0.021 nm/mm, and temperature sensitivities of 0.074 and 0.081 nm/°C are achieved, respectively.