High-Resolution OFDR with All Grating Fiber Combining Phase Demodulation and Cross-Correlation Methods

Area of Science:

• Fiber Optic Sensing
• Optical Metrology
• Materials Science

Background:

• Spatial resolution is crucial for Optical Frequency Domain Reflectometry (OFDR).
• Phase-sensitive OFDR (Φ-OFDR) offers high potential for spatial resolution but is susceptible to noise.
• Coherent fading and system noise cause fluctuations in Φ-OFDR results.

Purpose of the Study:

• To develop an OFDR-based strain sensing method with high spatial resolution.
• To overcome noise limitations in phase-sensitive OFDR.
• To achieve accurate and complete strain distribution measurement.

Main Methods:

• Combined phase demodulation (using frequency-shift averaging and rotating vector summation algorithms) with adaptive window cross-correlation analysis.
• FSAV and RVS algorithms suppress coherent fading noise for accurate strain localization.
• Adaptive cross-correlation window adjusts to continuous and uniform strain regions based on phase demodulation results.

Main Results:

• Achieved a spatial resolution of 0.27 mm for strain boundaries within a 100-700 με strain range.
• Demonstrated a root-mean-square error approaching 0.94% for strain measurement.
• Processing time of approximately 0.035 s for a 1.6 m demodulation length.

Conclusions:

• The proposed method provides precise spatial localization of strain boundaries and stable strain measurements.
• It effectively suppresses noise, enhancing the reliability of OFDR-based strain sensing.
• Demonstrates significant potential for high-resolution OFDR applications requiring accurate strain distribution analysis.