Interference fading suppression method for φ-OTDR based on time-distance dual-domain phase differential

Area of Science:

• Optical Engineering
• Signal Processing
• Fiber Optic Sensing

Background:

• Phase-sensitive optical time-domain reflectometry (φ-OTDR) systems are susceptible to interference fading.
• Fading, caused by phase randomness and environmental factors, degrades measurement accuracy.
• Existing methods struggle to address both noise- and vibration-induced fading simultaneously.

Purpose of the Study:

• To introduce a novel time-distance dual-domain phase differential (TDPD) method.
• To reconstruct constructive interference conditions in fading regions of φ-OTDR.
• To enhance the robustness and accuracy of phase demodulation in φ-OTDR systems.

Main Methods:

• The time-distance dual-domain phase differential (TDPD) method utilizes distance-domain vector superposition to suppress noise-dominated fading.
• Time-domain differential phase processing eliminates vibration-induced fading by reducing inter-wave phase differences.
• Temporal-neighboring phase unwrapping and integration recover the original phase waveform.

Main Results:

• Experimental validation on a 10 km fiber demonstrated accurate phase measurements for various vibrations (10 Hz, chirp, 0.1 Hz).
• The TDPD method achieved a signal-to-noise ratio (SNR) improvement of over 40 dB in vibration regions compared to conventional techniques.
• Simultaneous mitigation of both noise- and vibration-affected fading was successfully demonstrated.

Conclusions:

• The TDPD method provides a reliable solution for precise phase demodulation in φ-OTDR.
• This cost-effective and computationally efficient framework significantly improves SNR and measurement accuracy.
• TDPD addresses key limitations in current φ-OTDR systems, enabling more robust fiber optic sensing.