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

Area of Science:

• Fiber optics
• Optical sensing
• Interferometry

Background:

• Torsion sensing is crucial for various industrial and AI applications.
• Existing torsion sensors often lack directional sensitivity or are complex.
• Developing cost-effective and high-performance torsion sensors is an ongoing challenge.

Purpose of the Study:

• To develop a novel in-fiber Mach-Zehnder interferometer (MZI) based directional torsion sensor.
• To investigate the influence of offset splicing and fiber length on sensor performance.
• To achieve directional torsion measurement with high sensitivity and linearity.

Main Methods:

• Fabrication of an in-fiber MZI by sandwiching a two-mode fiber section between single-mode fibers using over core-offset splicing.
• Modulation of offset and fiber length to control fringe visibility.
• Experimental characterization of the sensor's response to varying torsion angles and directions.

Main Results:

• Achieved near-zero visibility at 0° rotation through fine offset modulation, enabling directional detection.
• Demonstrated recognition of counter-clockwise vs. clockwise torsion via fringe peak-to-dip reversal.
• Obtained a sensitivity of 21.485 dB/(rad/cm) with high linearity and low-temperature crosstalk (-40 to 40 rad/m).

Conclusions:

• The developed fiber torsion sensor offers directional measurement capabilities.
• The sensor is compact, easy to fabricate, and cost-effective.
• It shows significant potential for industrial monitoring and artificial intelligence applications.