Phase-sensitive optical time-domain reflectometric system based on a single-source dual heterodyne detection scheme

Area of Science:

• Photonics and Sensing Technologies
• Optical Metrology
• Fiber Optic Sensing

Background:

• Phase-sensitive optical time-domain reflectometry (ϕ-OTDR) is crucial for distributed fiber optic sensing.
• Existing ϕ-OTDR systems often struggle with residual frequency and phase fluctuations, limiting performance.
• Environmental factors and system components introduce noise that complicates vibration signal extraction.

Purpose of the Study:

• To propose and demonstrate a novel single-source dual heterodyne detection scheme for ϕ-OTDR.
• To improve the isolation of pure vibration signals from environmental and system-induced noise.
• To enhance the real-time performance and reliability of ϕ-OTDR systems.

Main Methods:

• Implementation of a single-source dual heterodyne detection scheme.
• Utilizing optical beat-frequency signals as a local oscillator to capture modulated frequency, drift, and phase fluctuations.
• Employing frequency mixing to extract the vibration signal, effectively canceling out unwanted spectral components.

Main Results:

• Achieved a spatial resolution of 9 m over a 24.6 km sensing fiber.
• Demonstrated a detectable frequency range from 5 Hz to 1.715 kHz.
• Obtained a signal-to-noise ratio greater than 23.5 dB, with parameters near theoretical maximums.

Conclusions:

• The novel dual heterodyne detection scheme significantly improves ϕ-OTDR system demodulation characteristics.
• The enhanced system exhibits superior performance and reliability for practical engineering applications.
• This approach effectively mitigates noise from clock synchronization, laser, acousto-optical modulator, and temperature variations.