Ultra-linear broadband optical frequency sweep for a long-range and centimeter-spatial-resolution OFDR

Area of Science:

• Photonics and Optical Sensing
• Metrology and Measurement Science
• Materials Science and Engineering

Background:

• Optical frequency domain reflectometry (OFDR) is crucial for high-resolution measurements.
• Achieving long-range and centimeter-spatial-resolution simultaneously in OFDR systems presents significant technical challenges.
• Nonlinear sweeping effects in lasers can degrade measurement accuracy and stability.

Purpose of the Study:

• To develop and demonstrate a long-range, centimeter-spatial-resolution OFDR system.
• To overcome limitations of nonlinear laser sweeping for stable, fast optical frequency sweeps.
• To validate the system's performance in distributed strain sensing applications.

Main Methods:

• Implemented an ultra-linear broadband optical frequency sweep using an optimized injection-locking system.
• Utilized a pre-distortion method to suppress nonlinear sweeping effects of distributed feedback (DFB) diode lasers.
• Achieved a high optical linear frequency sweep (LFS) with a 60 GHz range and 15 THz/s sweep rate.

Main Results:

• The developed OFDR system achieved a sampling spatial resolution of 1.71 mm.
• Demonstrated distributed strain sensing with high spatial resolutions of approximately 5 cm and 7 cm.
• Successfully performed measurements over extended ranges of 1 km and 2 km.

Conclusions:

• The proposed ultra-linear broadband optical frequency sweep enables high-performance OFDR.
• The system provides a robust solution for long-range, high-spatial-resolution distributed strain sensing.
• This advancement has significant implications for structural health monitoring and precision metrology.