Single-ended forward-transmission distributed sensing system based on chirped frequency-swept modulation.

Area of Science:

• Optoelectronics and Photonics
• Civil Engineering and Infrastructure Monitoring
• Distributed Sensing Technologies

Background:

• Urbanization necessitates advanced monitoring for mega-infrastructures and disaster prediction.
• Ultra-long-distance sensing is crucial for structural health and early warning systems.
• Existing methods face limitations in sensing distance and practical deployment.

Purpose of the Study:

• To develop a single-ended, forward-transmission distributed fiber-optic vibration sensing (FTDVS) system.
• To enable long-distance structural health monitoring and environmental sensing.
• To overcome challenges of single-ended probing and passive fiber termination.

Main Methods:

• Utilized single-sideband chirped frequency-swept modulation with an I/Q modulator.
• Implemented delay fibers for frequency-domain separation at the termination end.
• Employed digital filters to mitigate Rayleigh backscattering (RBS) and extract signals.

Main Results:

• Demonstrated robust performance over 120km sensing distance without inline amplification.
• Achieved 85m positioning accuracy despite RBS being 72 dB stronger than the signal.
• Successfully distinguished forward-propagating signals from unwanted paths.

Conclusions:

• The proposed FTDVS system offers a cost-effective and simplified solution for ultra-long-distance sensing.
• This technology supports distributed mapping and ground-truthing for smart city infrastructure and environmental monitoring.
• Paves the way for enhanced safety and management of critical infrastructure.