Liquid level and temperature sensor based on an asymmetrical fiber Mach-Zehnder interferometer combined with a fiber Bragg grating

A fiber optic sensor capable of simultaneous measurement of liquid level and temperature is proposed and demonstrated. The sensor is formed by the integration of an asymmetrical fiber Mach-Zehnder interferometer (aFMZI) with a fiber Bragg grating (FBG). The aFMZI was realized by concatenating a fiber taper and a lateral-shifted junction. By using the temperature sensing property of FBG, the liquid level sensor with dynamic temperature compensation can be achieved. For 10 pm wavelength resolution, a resolution of 0.15 cm in liquid level and 1.01 °C in temperature can be achieved. The prototype has the advantages of low fabrication cost and temperature compensated, which are desirable features in liquid level measurement.