Highly birefringent side-hole fiber Bragg grating for high-temperature pressure sensing

Area of Science:

• Optical Engineering
• Materials Science
• Sensor Technology

Background:

• High-temperature pressure sensing is critical for monitoring industrial processes in extreme environments.
• Existing sensors often face limitations in accuracy, durability, and operating temperature range.
• Fiber optic sensors offer potential advantages due to their immunity to electromagnetic interference and high-temperature resilience.

Purpose of the Study:

• To develop and demonstrate a novel high-temperature pressure sensor.
• To utilize a highly birefringent fiber Bragg grating (Hi-Bi FBG) inscribed in a dual side-hole fiber (DSHF) for enhanced pressure sensitivity.
• To achieve accurate pressure measurements at temperatures up to 700°C.

Main Methods:

• Fabrication of a Hi-Bi FBG in a DSHF using femtosecond laser-induced sawtooth structures.
• Etching the DSHF with hydrofluoric acid to enlarge air holes and increase pressure sensitivity.
• Utilizing Bragg resonance and birefringence-induced peak splits for pressure and temperature discrimination.
• Demonstrating a wavelength-division-multiplexed (WDM) Hi-Bi FBG array for quasi-distributed sensing.

Main Results:

• Successfully inscribed a Hi-Bi FBG with high birefringence (up to 1.8 × 10⁻³) in an etched DSHF.
• Achieved high-pressure sensitivity of -21.2 pm/MPa at temperatures up to 700°C.
• Demonstrated simultaneous temperature and pressure discrimination by analyzing Bragg wavelength shifts and peak splits.
• Constructed a WDM Hi-Bi FBG array for quasi-distributed sensing up to 3 MPa.

Conclusions:

• The femtosecond laser-inscribed Hi-Bi FBG in DSHF is a viable and promising technology for high-temperature pressure sensing.
• The sensor exhibits high sensitivity and the ability to differentiate between temperature and pressure effects.
• The proposed sensor is suitable for demanding applications in aerospace, nuclear reactors, and the petrochemical industry.