Multi-longitudinal mode fiber laser digital vibration-sensing system based on a multi-carrier modulation/demodulation...

Area of Science:

• Photonics and Sensing Technology
• Digital Signal Processing

Background:

• Fiber laser sensors offer potential for vibration detection.
• Existing demodulation techniques can limit sensitivity and accuracy, especially for low-frequency or weak signals.

Purpose of the Study:

• To develop and demonstrate a novel digital vibration-demodulation system for multi-longitudinal mode fiber laser sensors (MLMFLS).
• To improve the signal-to-noise ratio (SNR), stability, and accuracy of vibration sensing, particularly for low-frequency and weak signals.

Main Methods:

• Utilized a multi-longitudinal mode fiber laser sensor (MLMFLS) system.
• Implemented a digital modulation/demodulation technique with multiple beat frequency signals (BFS) as carriers.
• Employed a multi-channel digital down-conversion technique using a digital universal software radio peripheral (USRP) for simultaneous demodulation.
• Superposed demodulated signals from different channels via the USRP to enhance SNR.

Main Results:

• Achieved simultaneous demodulation of vibration signals modulated on multiple BFS.
• Significantly improved the signal-to-noise ratio (SNR) of the output vibration signal.
• Demonstrated excellent low-frequency vibration-sensing capability.
• Confirmed high stability and accuracy of the developed sensing system.

Conclusions:

• The proposed digital vibration-demodulation system for MLMFLS is the first of its kind.
• The system offers a simple structure, high SNR, and enhanced stability and accuracy for vibration sensing.
• This approach is particularly effective for detecting extremely low-frequency or weak vibration signals.