High SNR Φ-OTDR with Multi-Transverse Modes Heterodyne Matched-Filtering Technology

Area of Science:

• Optoelectronics
• Fiber Optics Sensing

Background:

• Phase-sensitive optical time domain reflectometer (Φ-OTDR) offers distributed dynamic linear response to external disturbances.
• Weak Rayleigh Backscattering coefficient limits the signal-to-noise ratio (SNR) in Φ-OTDR systems.

Purpose of the Study:

• To improve the system SNR of Φ-OTDR by introducing multi-transverse modes heterodyne matched-filtering technology.
• To enhance capture efficiency and nonlinear threshold using few-mode fibers and heterodyne matched-filtering.

Main Methods:

• Integration of multi-transverse modes in few-mode fibers to increase capture efficiency and nonlinear threshold.
• Application of digital heterodyne matched filtering to enlarge probe pulse width without sacrificing spatial resolution.
• Simultaneous application of multi-transverse modes integration and digital heterodyne matched filtering for SNR improvement.

Main Results:

• Experimental results demonstrate a noise floor reduction of 11.4 dB.
• The target signal integrity was maintained during the noise floor reduction.
• The proposed method successfully improved the SNR of the Φ-OTDR system.

Conclusions:

• The combined multi-transverse modes integration and digital heterodyne matched filtering method is effective in enhancing Φ-OTDR SNR.
• This advancement holds potential for improving distributed acoustic sensing (DAS) in marine acoustic and seismic detection.