Fiber-optic distributed acoustic sensor based on a chirped pulse and a non-matched filter

Area of Science:

• Optoelectronics
• Fiber Optic Sensing
• Signal Processing

Background:

• Traditional distributed acoustic sensing (DAS) systems, such as those using phase-sensitive optical time-domain reflectometry (ϕ-OTDR), face limitations in spatial resolution and sensing distance due to fading issues.
• The Rayleigh phase method, commonly used in ϕ-OTDR, suffers from fading, which hinders accurate quantitative strain demodulation.
• Overcoming the trade-off between spatial resolution and sensing distance is crucial for advancing DAS technology.

Purpose of the Study:

• To propose and demonstrate a novel distributed acoustic sensing (DAS) scheme.
• To address and overcome the fading problem inherent in traditional DAS methods.
• To improve the spatial resolution and sensing distance capabilities of DAS systems.

Main Methods:

• Utilizing an optical chirped pulse and a non-matched filter method to determine spatial resolution.
• Employing the Rayleigh interference pattern method for quantitative strain demodulation, thereby eliminating fading.
• Implementing a distributed acoustic sensor (DAS) system for experimental validation.

Main Results:

• Demonstrated a DAS system with 2-m spatial resolution and a 10-km sensing range.
• Achieved a strain response bandwidth of 5 kHz, primarily limited by fiber length.
• Successfully detected nε-scale strain signals at the far end of the fiber with a high signal-to-noise ratio (SNR) of 35 dB.

Conclusions:

• The proposed DAS scheme effectively overcomes the fading problem and the traditional trade-off between spatial resolution and sensing distance.
• The system offers high spatial resolution and long-distance sensing capabilities, suitable for various applications.
• The demonstrated performance, including nε-scale strain detection with high SNR, highlights the potential of this advanced DAS technology.