Low Computational Cost Distributed Acoustic Sensing Using Analog I/Q Demodulation.

Area of Science:

• Optoelectronics
• Signal Processing
• Sensing Technology

Background:

• Distributed acoustic sensing (DAS) using phase-sensitive optical time-domain reflectometry (Φ-OTDR) is crucial for acoustic measurements.
• Current phase demodulation methods, like digital coherent detection, impose a significant computational burden.
• Reducing computational cost is vital for widespread DAS adoption.

Purpose of the Study:

• To introduce analog I/Q demodulation into Φ-OTDR-based DAS systems.
• To reduce the computational complexity and data volume of DAS systems.
• To provide a cost-effective solution for sensitive acoustic sensing applications.

Main Methods:

• Implemented analog I/Q demodulation to directly obtain beat signal components.
• Eliminated the need for extensive digital signal processing.
• Utilized lower sampling frequencies for data acquisition cards.

Main Results:

• Achieved direct acquisition of I and Q components, drastically cutting computational cost.
• Demonstrated that spectrum aliasing does not impact demodulation, allowing lower sampling rates.
• Experimental results confirmed good linearity and a wide frequency response range.
• Successfully recovered acoustic signals sensed by optical fibers.

Conclusions:

• Analog I/Q demodulation offers a computationally efficient alternative for Φ-OTDR-based DAS.
• The proposed system effectively reduces computational and data handling requirements.
• This approach presents a promising solution for distributed acoustic sensing in cost-sensitive applications.