Abstract

A novel scheme for liquid level detection using an all-fiber Mach–Zehnder interferometer, based on two up-tapers, is proposed and experimentally investigated. The effective refractive indices of the axisymmetric modes ${\mathrm{LP}}_{0n}$ are analyzed while it is partly immersed in liquid. The sensitivity of the sensor is greatly dependent on the fiber length between the two up-tapers, as well as the order of the cladding modes through the calculation. The experimental results show that the sensitivity of the Mach–Zehnder interferometer reaches a 22.5 nm wavelength shift per meter of level change with the middle fiber length of 14.3 cm. The proposal might be attractive since the up-tapered liquid level sensor could easily be fabricated and used for a large measuring range.

© 2013 Optical Society of America

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