Fiber-optic distributed acoustic sensor utilizing LiNbO₃ straight through waveguide phase modulator

Area of Science:

• Optoelectronics
• Fiber Optic Sensing
• Acoustic Detection

Background:

• Traditional homodyne detection systems for distributed acoustic sensing (DAS) face limitations such as low modulation frequency and unstable performance associated with piezoelectric transducers (PZT).
• Existing systems are often constrained by the pulse repetition frequency, limiting their detection capabilities.

Purpose of the Study:

• To present a novel fiber-optic distributed acoustic sensor (DAS) system.
• To introduce a new phase generation carrier (PGC) modulation module utilizing a LiNbO3 straight through waveguide phase modulator.
• To overcome the limitations of traditional PZT-based systems in terms of modulation frequency and performance stability.

Main Methods:

• The study employs a phase-sensitive optical time domain reflectometer (Φ-OTDR) based system.
• A LiNbO3 straight through waveguide phase modulator is used as the phase generation carrier (PGC) modulation module.
• The sensitive principle and phase demodulation method of the proposed system are described.

Main Results:

• The novel DAS system accurately demodulates weak acoustic signals.
• Achieved performance metrics include a noise level below 4.2×10⁻³ rad/√Hz and a signal-to-noise ratio (SNR) greater than 16 dB.
• The system demonstrates a spatial resolution of 10 m and a theoretical detection frequency of up to 25 kHz over a 2 km sensing fiber.

Conclusions:

• The developed fiber-optic DAS system offers a significant advancement over traditional PZT-based methods.
• It provides a high-frequency response, low cost, and long-distance detection capability.
• This technology presents a promising alternative for various DAS applications, potentially replacing PZT modules.