Coded phase-sensitive OTDR with delayed polarization multiplexing for a WFBG array

Area of Science:

• Optoelectronics
• Fiber optic sensing
• Signal processing

Background:

• Polarization fading significantly degrades phase-sensitive optical time-domain reflectometry (φ-OTDR) performance.
• Effective suppression of polarization fading is crucial for reliable φ-OTDR applications.

Purpose of the Study:

• To propose and demonstrate a novel scheme to combat polarization fading in φ-OTDR.
• To achieve polarization-independent phase variation measurements for vibration detection.

Main Methods:

• A simple transceiver structure is employed, utilizing polarization diversity via delayed polarization multiplexing.
• Aperiodic autocorrelation of a pseudorandom binary sequence is used to extract fiber sensing matrix components.
• Jones matrix components are directly obtained at autocorrelation peaks without complex computations.

Main Results:

• The proposed scheme successfully suppresses polarization fading, enabling polarization-independent phase variation measurements.
• Experimental demonstration on a weak fiber Bragg grating (WFBG) array showed high crosstalk rejection (>50 dB).
• A high dynamic range (>30 dB) was achieved, indicating robust sensing capabilities.

Conclusions:

• The novel scheme effectively mitigates polarization fading in φ-OTDR systems.
• The method offers a simple yet powerful solution for polarization-independent vibration sensing.
• The approach is practical and does not require precise matching between delay times and sensor spacing.