Optical fiber twist sensor based on a double-helix structure and quasi-distributed displacement system

Area of Science:

• Fiber Optic Sensing
• Mechanical Engineering
• Signal Processing

Background:

• Cable-type sensor arrays suffer from axial torsion, leading to vector signal projection errors.
• Accurate characterization of torsional deformation is crucial for reliable sensor performance.
• Traditional optical fiber twist sensors exhibit measurement errors that accumulate with sensor length.

Purpose of the Study:

• To introduce a novel dual-helix optical fiber twisting measurement method.
• To overcome the limitations of accumulating errors in conventional fiber optic twist sensors.
• To enable accurate torsional deformation measurement in long-distance cable-style sensor arrays.

Main Methods:

• Applied Saint Venant's theory to develop a fiber twist sensing model.
• Constructed a quasi-distributed fiber displacement measurement system using dual modulation with a Mach-Zehnder modulator (MZM).
• Experimental verification involved two optical fibers wound helically in opposite directions on a silicone substrate.

Main Results:

• The proposed sensor effectively measures twisting angles within a range of ±90°.
• Achieved a sensitivity coefficient of 40.76 kHz/° and a measurement accuracy of 0.39°.
• Demonstrated that twisting error does not accumulate with sensor length and effectively suppresses common-mode noise (CMN).

Conclusions:

• The dual-helix optical fiber method provides accurate and length-independent torsion measurement.
• This technique significantly enhances the reliability of torsional deformation characterization.
• The approach holds substantial potential for long-distance underwater cable-style sensor array applications.