Improving OFDR sensing performance based on SEFR in both reference and measurement stages

Area of Science:

• Optical Engineering
• Metrology
• Sensing Technology

Background:

• Optical Frequency Domain Reflectometry (OFDR) performance is limited by sensing point misalignment due to random laser frequency sweep range (LFSR) and sweep nonlinearity.
• Accurate distributed strain measurement is crucial in various engineering applications.

Purpose of the Study:

• To propose and validate a novel synchronous equal frequency resampling (SEFR) method for OFDR.
• To simultaneously compensate for random LFSR and sweep nonlinearity in OFDR systems.
• To improve the sensing distance and accuracy of OFDR for distributed strain measurement.

Main Methods:

• Development of a synchronous equal frequency resampling (SEFR) method.
• Construction of a new linear frequency sequence for signal resampling.
• Application of SEFR to both reference and measurement stages in OFDR.
• Evaluation of SEFR's impact on Phase Demodulation (PD) and Cross-Correlation Demodulation (CD) based OFDR.

Main Results:

• SEFR successfully eliminates sensing point misalignment and nonlinear frequency intervals.
• For PD-based OFDR, sensing distance extended to 70 m with a 16-fold reduction in strain RMSE under worst-case LFSR differences.
• For CD-based OFDR, sensing distance extended from 6.8 m to 70 m with a 41-fold reduction in strain RMSE under worst-case LFSR differences.

Conclusions:

• The proposed SEFR method significantly enhances OFDR performance by addressing key limitations.
• SEFR offers substantial improvements in both sensing distance and measurement accuracy for distributed strain sensing.
• This method provides a robust solution for high-performance OFDR applications.