Temperature compensated fiber-optic liquid level sensor by micro-sphere based in-line Michelson interferometer

Abstract

In this paper, a novel micro-sphere based in-line Michelson interferometer is proposed and completed experimentally through arc-discharge technique. The light field distributions are theoretically investigated to gain optimal core offset and diameter of micro-sphere. Multiple fabricated samples are compared and the comprehensive tests are then performed in terms of liquid level and temperature. The experimental results show that obvious blue shift of fringes is demonstrated with the rise of liquid level and the average sensitivity reaches 62.6 pm/mm with high linearity in the range of 0–40 mm. Moreover, owing to highly-consistent temperature response (∼99.5%), the crosstalk caused by ambient temperature is eliminated by differential method and the measurement error is compressed within 1.33%. Due to the merits of compactness, low cost, ease of fabrication and operation, our sensor is very potential in the liquid-level related engineering applications.