Two-mode fiber based directional torsion sensor with intensity modulation and 0° turning point

In this paper, we report a novel in-fiberMach-Zehnder interferometer based directional torsion sensor, in which a section of two-mode fiber is sandwiched between two single mode fibers by over core-offset splicing technique. The variety of fringe visibility demonstrates the strong dependence on offset and fiber length. For the first time the near zero visibility at 0 degrees rotating state is obtained by fine offset-modulation. The experimental results show that, with 0 degrees turning point, the counter-clockwise to the clockwise direction can be recognized by the reversal from peak to dip of fringes. Moreover, a competitive sensitivity of 21.485 dB/(rad/cm) is gained with high linearity and low-temperature crosstalk in the range from -40 rad/m to 40 rad/m. Without any pre-twisting, our fiber torsion sensor is small size, ease of fabrication, cost efficiency and very potential in the applications of industrial and artificial intelligence. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement