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    Area of Science:

    • Optoelectronics
    • Signal Processing
    • Fiber Optic Sensing

    Background:

    • Phase-sensitive optical time domain reflectometry (ϕ-OTDR) systems are limited in their maximum detectable vibration frequency by the round-trip time of light pulses.
    • Conventional ϕ-OTDR uses uniform laser pulse intervals, restricting the frequency response range.

    Purpose of the Study:

    • To overcome the frequency response limitations of ϕ-OTDR.
    • To develop a method for broadening the detectable vibration frequency range in ϕ-OTDR systems.
    • To enable the detection of sparse, wideband-frequency vibration signals.

    Main Methods:

    • Implemented a novel sub-Nyquist additive random sampling (sNARS) technique by randomly modulating laser pulse intervals.
    • Optimized the sNARS method through theoretical analysis and Monte Carlo simulations for a 10 km ϕ-OTDR system.
    • Verified the method's effectiveness in identifying and reconstructing wideband sparse signals.

    Main Results:

    • The sNARS method successfully broadens the vibration frequency response range of ϕ-OTDR.
    • Experimental results confirmed the capability to identify and reconstruct wideband sparse signals.
    • The optimized sNARS approach demonstrated significant improvements in vibration frequency detection.

    Conclusions:

    • Randomly modulating pulse intervals in ϕ-OTDR, creating sNARS, effectively expands the system's vibration frequency response range.
    • This technique is crucial for advancing sparse-wideband-frequency vibration signal detection applications.
    • The study provides a significant advancement in the capabilities of ϕ-OTDR for vibration monitoring.