An Intensity-Modulated In-Fiber Liquid Lever Sensor Based on Intermodal Michelson Interferssometer

Abstract

A compact in-fiber Michelson interferometer (MI) for liquid level measurement is proposed and demonstrated. The interferometer is fabricated by simply splicing a section of multimode fiber (MMF) with a standard singlemode fiber (SMF). The reflection spectrum of the MI is dependent on the portion of the length of the MMF which is immersed in liquid. The sensing characteristics of the liquid level and temperature are theoretically and experimentally investigated. The experimental results show that the liquid level sensitivity is −1.20 dB/mm when the liquid is water, and the liquid level measurement error induced by temperature is 0.004 mm/°C. The advantages of temperature-immune, cost-effective and reflective intensity demodulation offer the prospective application in chemical and petroleum industrial sensing.