Sub-100 fε resolution strain sensing based on an optical fiber frequency comb.

Area of Science:

• Photonics and Sensing Technology
• Optical Fiber Sensing
• Metrology

Background:

• Accurate strain measurement is critical for structural health monitoring and geophysical applications.
• Existing optical fiber sensors face limitations in resolution, dynamic range, or spectral range.

Purpose of the Study:

• To develop and demonstrate a high-resolution optical fiber strain sensing system.
• To leverage optical frequency comb (OFC) beat-frequency demodulation for enhanced strain detection capabilities.

Main Methods:

• Utilized a fiber Fabry-Perot interferometer (FFPI) as the strain sensing element.
• Employed optical frequency comb (OFC) beat-frequency demodulation to convert optical frequency shifts to radio frequency (RF) signals.
• Investigated both stabilized and free-running OFC configurations for static and dynamic strain sensing.

Main Results:

• Achieved a static strain resolution of 247 pε and a dynamic strain resolution of 87 fε/Hz^1/2 at 8 kHz.
• Demonstrated a large spectral range of 10 kHz, enabling operation away from low-frequency noise.
• Obtained a static strain resolution of 630 pε using a free-running OFC with active frequency sweeping.

Conclusions:

• The developed OFC-based strain sensing system offers high resolution, a large dynamic strain measurement range, and a wide spectral range.
• The system's portability and moderate cost make it a promising tool for geophysical research.
• Beat-frequency demodulation with OFC provides a robust method for high-precision optical fiber strain sensing.