Torsion bidirectional sensor based on tilted-arc long-period fiber grating

Area of Science:

• Fiber optics
• Optical sensing
• Nanotechnology

Background:

• Fiber torsion sensors are crucial but face challenges in distinguishing torsion direction.
• Existing methods often require complex fabrication or specialized fiber structures.
• Limited sensitivity and fabrication complexity hinder widespread application.

Purpose of the Study:

• To design and fabricate a novel long-period fiber grating (LPFG) for accurate bidirectional torsion sensing.
• To develop a cost-effective and highly sensitive fiber optic torsion sensor.
• To overcome limitations of existing fiber torsion sensors in direction distinction and sensitivity.

Main Methods:

• A novel LPFG was designed and fabricated using tilted-arc grids in a standard single-mode fiber via CO2 laser scanning.
• Theoretical analysis was performed to understand the relationship between structure parameters (radius, tilt angle) and torsion response.
• Experimental testing was conducted to evaluate the sensor's ability to distinguish bidirectional torsion and measure sensitivity.

Main Results:

• The fabricated tilted-arc LPFG demonstrated the ability to distinguish bidirectional torsion.
• The sensor exhibited high sensitivity, with a maximum value reaching 0.514 nm/(rad·m⁻¹).
• The asymmetrical grid structure induced chirality, enabling direction-distinguishing capabilities without complex fabrication steps.

Conclusions:

• The novel tilted-arc LPFG offers a simple fabrication process, high sensitivity, and direction-distinguishing ability for torsion sensing.
• This sensor design presents a significant advancement over traditional tilted LPFGs and twisted fiber structures.
• The developed LPFG sensor holds potential for practical applications in directional torsion field monitoring.