Multi-vibration detection by probe pulses with ergodic SOPs in a POTDR system.

Area of Science:

• Optical Engineering
• Fiber Optic Sensing
• Signal Processing

Background:

• Polarization Optical Time Domain Reflectometers (POTDR) detect fiber vibrations via changes in Rayleigh backscattered light's state of polarization (SOP).
• Traditional POTDR systems suffer from high misdiagnosis rates when multiple simultaneous vibrations occur due to random fiber birefringence.

Purpose of the Study:

• To propose and validate a novel POTDR implementation to overcome the limitations of traditional systems in multi-vibration detection.
• To significantly reduce the misdiagnosis rate in detecting simultaneous vibrations along a sensing fiber.

Main Methods:

• Utilizing probe pulses with ergodic states of polarization (SOPs).
• Acquiring a series of vibration spectra by sweeping the probe pulse's SOP.
• Summing vibration spectra to achieve immunity to fiber birefringence for vibration analysis.
• Conducting numerical simulations and experimental validation with uniform and random SOP distributions.

Main Results:

• The proposed POTDR system demonstrates a greatly reduced misdiagnosis rate for detecting multi-vibrations with different frequencies.
• Successful detection of more than two simultaneous vibrations with the same frequency using POTDR, a first to our knowledge.
• The summation of vibration spectra effectively mitigates the impact of random birefringence.

Conclusions:

• The novel POTDR implementation with ergodic SOP probe pulses effectively addresses the challenge of multi-vibration detection in sensing fibers.
• This approach offers enhanced accuracy and reliability for fiber optic sensing applications, particularly in complex vibration scenarios.
• The technique enables robust identification of multiple vibration sources, even those with identical frequencies.