Overcoming acoustic crosstalk in the BOTDA sensor with a bidirectional frequency-modulated probe

Area of Science:

• Optical Fiber Sensing
• Photonics
• Signal Processing

Background:

• Conventional Brillouin optical time-domain analyzers (BOTDA) using frequency-modulated probes (FMP) mitigate non-local effects.
• However, acoustic crosstalk between different frequencies in FMP-BOTDA systems introduces Brillouin frequency shift (BFS) measurement errors.
• These errors reduce the overall certainty and reliability of measurements in distributed fiber sensing.

Purpose of the Study:

• To propose and validate a novel BOTDA scheme to overcome acoustic crosstalk limitations.
• To enhance measurement efficiency and accuracy in long-haul fiber optic sensing.
• To eliminate Brillouin frequency shift (BFS) estimation errors caused by crosstalk.

Main Methods:

• Implementation of a bidirectional frequency-modulated probe (BFMP) within the BOTDA framework.
• BFMP generates crosstalk of equal magnitude and opposite direction to enable mutual compensation.
• Experimental validation using a 117.46-km fiber optic sensor link.

Main Results:

• The proposed BFMP-BOTDA scheme effectively eliminates BFS estimation errors.
• Measurement efficiency is improved by reducing the pulse interval of the coded sequence to approximately 500 ns.
• BFS estimation errors were reduced to approximately 2.2 MHz over the entire 117.46-km sensing link.

Conclusions:

• The bidirectional frequency-modulated probe (BFMP) is a viable solution for mitigating crosstalk in BOTDA systems.
• This technique significantly enhances the accuracy and efficiency of distributed fiber optic sensing.
• The BFMP-BOTDA scheme offers a robust method for precise strain and temperature monitoring over extended distances.