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Dynamic phase extraction in a modulated double-pulse ϕ-OTDR sensor using a stable homodyne demodulation in direct
Optics Express
|February 7, 2018
Summary
We developed a stable homodyne phase demodulation technique for phase-sensitive optical time-domain reflectometry (ϕ-OTDR) using a double-pulse probe. This method accurately quantifies dynamic phase changes in optical fibers, even with external impacts.
Area of Science:
- Optoelectronics
- Fiber optic sensing
- Signal processing
Background:
- Phase-sensitive optical time-domain reflectometry (ϕ-OTDR) is crucial for distributed sensing.
- Existing demodulation techniques often struggle with light intensity fluctuations and modulation depth variations.
- A robust and simple demodulation method is needed for practical ϕ-OTDR applications.
Purpose of the Study:
- To propose and demonstrate a stable homodyne phase demodulation technique for ϕ-OTDR.
- To develop a method robust against intensity fluctuations and independent of modulation depth.
- To enable accurate quantification of distributed dynamic phase changes.
Main Methods:
- Utilized a double-pulse probe with selective phase modulation of one pulse to create a carrier.
- Employed a simple direct detection receiver.
- Implemented an enhanced phase demodulation scheme suitable for analogue signal processing.
Main Results:
- Achieved stable homodyne phase demodulation in a ϕ-OTDR system.
- Demonstrated quantification of a 2 kHz dynamic phase change at 1.5 km distance on standard single-mode fiber.
- Obtained a signal-to-noise ratio (SNR) of approximately 24 dB.
- Showcased demodulated nonlinear response spectrum consistent with FBG sensor data.
Conclusions:
- The proposed technique provides a stable and robust solution for phase demodulation in ϕ-OTDR.
- The method is effective for distributed sensing of dynamic phase changes induced by external impacts.
- This technique offers a convenient approach for analogue signal processing in distributed fiber optic sensing.
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