Raman-assisted Brillouin optical time-domain analysis with sub-meter resolution over 100 km

Area of Science:

• Fiber Optic Sensing
• Optical Metrology
• Signal Processing

Background:

• Long-distance Brillouin Optical Time Domain Analysis (BOTDA) faces challenges in achieving sub-meter resolution.
• Issues include resolution-uncertainty trade-offs, nonlinear effects like self-phase modulation, and signal degradation from fiber attenuation and depletion.

Purpose of the Study:

• To demonstrate sub-meter resolution in BOTDA over extended distances (100 km).
• To overcome the inherent limitations hindering high-resolution BOTDA.
• To showcase the detection of small-scale features in optical fibers.

Main Methods:

• Integration of Raman assistance to improve signal-to-noise ratio.
• Application of differential pulse-width pair (DPP) measurements for enhanced resolution.
• Implementation of a novel numerical de-noising algorithm to process the acquired data.

Main Results:

• Successfully achieved sub-meter resolution for BOTDA systems.
• Demonstrated effective operation over a 100 km fiber optic link.
• Successfully detected a localized 0.5-meter 'hot-spot' feature, even in challenging conditions of low contrast.

Conclusions:

• The combination of Raman assistance, DPP measurements, and advanced numerical processing is effective for high-resolution, long-distance BOTDA.
• This approach overcomes previous resolution limitations in BOTDA.
• Enables precise detection of small-scale anomalies in long-haul fiber optic sensing applications.