Quantitative amplitude-measuring Φ-OTDR with pε/√Hz sensitivity using a multi-frequency pulse train

Area of Science:

• Optical Engineering
• Sensing Technology
• Materials Science

Background:

• Distributed strain sensing is crucial for structural health monitoring.
• Existing phase-sensitive optical time domain reflectometry (PhOTDR) systems have limitations in sensitivity and power.

Purpose of the Study:

• To develop a novel amplitude-measuring Rayleigh-based sensor for quantitative distributed strain measurements.
• To improve sensor sensitivity and overcome limitations of standard PhOTDR systems.

Main Methods:

• Utilizing frequency multiplexing to inject 10 frequency-shifted pulses simultaneously into the fiber.
• Employing amplitude tracking of Rayleigh backscattered light from multiple pulses to recover strain.
• Implementing a sensor with 10 km fiber length, 12 m spatial resolution, and 5 kHz bandwidth.

Main Results:

• Achieved a noise floor of 1.5 pε/√Hz, demonstrating high sensitivity.
• The sensor operates with a dynamic range of 80 dB at 1 kHz.
• Demonstrated high linearity and immunity to interference fading.

Conclusions:

• The developed sensor offers enhanced sensitivity and quantitative distributed strain measurement capabilities.
• The frequency-multiplexing approach enables higher average input power, improving performance.
• This technology presents a robust solution for accurate strain monitoring in various applications.