A Phase-Sensitive Optical Time Domain Reflectometry with Non-Uniform Frequency Multiplexed NLFM Pulse.

Area of Science:

• Optical Fiber Sensing
• Acoustic Sensing Technology
• Signal Processing in Photonics

Background:

• Distributed optical fiber sensing faces challenges in extending sensing distances while improving spatial resolution and frequency response.
• Existing methods like pulse compression and frequency division multiplexing have limitations in bandwidth utilization and hardware costs.

Purpose of the Study:

• To introduce an innovative distributed optical fiber acoustic sensing system that optimizes spectral resource utilization.
• To enhance spatial resolution, frequency response range, and reduce hardware costs in optical fiber sensing.

Main Methods:

• Combines compressed pulses with non-uniform frequency division multiplexing (FDM) and non-linear frequency modulation (NFM).
• Continuously injects NFM detection pulses across various frequency ranges.
• Employs non-uniform FDM to augment vibration frequency response and NFM to reduce crosstalk and suppress sidelobes.

Main Results:

• Achieved a spatial resolution of approximately 5 m over a 16.3 km optical fiber.
• Expanded the frequency response range from 1 to 20 kHz.
• Successfully multiplexed eight frequencies within a 120 MHz bandwidth, demonstrating improved spectral efficiency.

Conclusions:

• The developed system significantly advances spatial resolution and frequency response in distributed optical fiber acoustic sensing.
• Optimized spectral resource utilization and reduced hardware costs, making it suitable for practical engineering applications.
• The combination of NFM and non-uniform FDM offers a robust solution for overcoming limitations in current sensing technologies.