Compact fiber strain sensor fabricated by a CO₂ laser.

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Materials Science

Background:

• Long Period Fiber Gratings (LPFGs) are crucial for optical sensing applications.
• Existing LPFG fabrication methods face limitations in sensitivity and size.
• Strain and temperature monitoring require highly sensitive and stable sensor technologies.

Purpose of the Study:

• To propose and demonstrate a novel Parallel Inclined Planes Long Period Fiber Grating (PIP-LPFG) for enhanced strain measurement.
• To investigate the fabrication process and performance characteristics of the PIP-LPFG.
• To evaluate the strain and temperature sensitivity of the proposed sensor.

Main Methods:

• Fabrication of the PIP-LPFG using a high-frequency CO2 laser on a single-mode fiber (SMF).
• Periodic parallel inclined planes were created on the SMF surface, inducing large-area Refractive Index Modulation (RIM).
• Experimental testing to measure strain response and temperature sensitivity within specific dynamic ranges.

Main Results:

• The PIP-LPFG achieved a miniature length of 3.9 mm.
• High strain sensitivity of 116 pm/µε was recorded in the 0-425 µε dynamic range.
• The sensor exhibited good repeatability and stability in strain response.
• Temperature sensitivity was measured at 54.7 pm/°C within the 30-170°C dynamic range.

Conclusions:

• The novel PIP-LPFG structure significantly enhances strain sensitivity.
• The compact size and high sensitivity make PIP-LPFG suitable for various strain measurement applications.
• The sensor demonstrates robust performance with good stability and minimal temperature interference.