Interference fading suppression in φ-OTDR using space-division multiplexed probes.

Area of Science:

• Optical Engineering
• Fiber Optics Communications
• Signal Processing

Background:

• Phase-sensitive optical time domain reflectometry (φ-OTDR) is crucial for high-resolution distributed sensing.
• Interference fading significantly degrades φ-OTDR performance, limiting its practical applications.
• Existing methods to suppress fading often involve complex modulation techniques.

Purpose of the Study:

• To propose and demonstrate a novel interference fading suppression method for φ-OTDR.
• To leverage space-division multiplexing (SDM) with multiple spatial modes for improved robustness.
• To reduce the complexity of φ-OTDR systems by avoiding frequency or phase modulation.

Main Methods:

• Utilized space-division multiplexed (SDM) pulse probes comprising three spatial modes (LP01, LP11a, LP11b) in a few-mode fiber.
• Experimentally characterized Rayleigh backscattering light from distinct spatial modes.
• Compared the performance of φ-OTDR systems using single versus multiple SDM probes.

Main Results:

• Demonstrated that Rayleigh backscattering waveforms from different spatial modes are distinct and independent.
• Showed that spatial differences in fading positions across modes enable effective fading suppression.
• Statistical analysis confirmed significant reduction in fading probabilities over fiber length and time using multiple SDM probes.

Conclusions:

• The proposed SDM-based method effectively suppresses interference fading in φ-OTDR.
• This approach offers simplicity, high effectiveness, and reliability compared to traditional modulation techniques.
• Introducing SDM to φ-OTDR significantly enhances its performance and practical viability.