Fiber-optic polarimetric strain sensor with three-wavelength digital phase demodulation

Area of Science:

• Optoelectronics
• Fiber Optic Sensors
• Materials Science

Background:

• Fiber-optic sensors offer advantages in harsh environments.
• Polarimetric sensors utilize light polarization for measurements.
• Accurate strain sensing is crucial for structural health monitoring.

Purpose of the Study:

• To investigate a fiber-optic polarimetric strain sensor with a 10-cm sensing length.
• To evaluate a three-wavelength passive quadrature digital phase demodulation technique.
• To assess the sensor's performance in quasi-static strain sensing applications.

Main Methods:

• Utilized a superluminescent diode light source and narrow-band interference filters.
• Employed real-time processing of interference intensities with an arctan-phase-stepping algorithm.
• Performed quasi-static strain sensing on a composite reinforced plastic rod.

Main Results:

• Achieved a measured displacement sensitivity of 125 mrad/µm, closely matching theoretical values.
• Demonstrated a linearity of the phase-strain characteristic of approximately 1%.
• Obtained a strain resolution of 2.5 microstrain (µε) despite low fringe contrast.

Conclusions:

• The developed fiber-optic polarimetric strain sensor provides accurate and reliable strain measurements.
• The three-wavelength passive quadrature digital phase demodulation technique is effective for strain sensing.
• The sensor shows potential for applications requiring high-resolution strain monitoring.