Static DFOS: pushing towards the limits of chirped-pulse phase-sensitive OTDR.

Area of Science:

• Sensing Technologies
• Optical Fiber Sensing
• Metrology

Background:

• Phase-sensitive optical time domain reflectometry (Φ-OTDR) enables distributed measurements of strain and temperature along optical fibers.
• Chirped-pulse (CP) Φ-OTDR, a relative measurement technique, faces challenges with accumulating errors in integrated signals, degrading slowly varying measurements.
• Existing methods to achieve absolute measurements require impractically high wavelength tuning resolutions.

Purpose of the Study:

• To address the limitations of Chirped-pulse (CP) Φ-OTDR for accurate distributed sensing.
• To demonstrate a method for overcoming the apparent resolution limits in CP-Φ-OTDR.
• To enable absolute strain and temperature measurements using Φ-OTDR techniques.

Main Methods:

• Theoretical description of CP-Φ-OTDR signal processing.
• Numerical simulations to validate theoretical models.
• Experimental validation using optical fiber sensing setups.

Main Results:

• The apparent limitation in CP-Φ-OTDR resolution is identified as noise-related.
• A novel approach leveraging the spectral content of the chirp is proposed and validated.
• The proposed method successfully overcomes previous resolution constraints.

Conclusions:

• The spectral content of the chirp can be utilized to overcome noise-related limitations in CP-Φ-OTDR.
• This advancement enables absolute strain and temperature measurements with improved accuracy.
• The findings pave the way for practical industrial applications of advanced Φ-OTDR systems.