Instability Compensation of Recording Interferometer in Phase-Sensitive OTDR.

Area of Science:

• Optoelectronics
• Optical Sensing
• Metrology

Background:

• Phase-sensitive optical time domain reflectometry (OTDR) is crucial for fiber optic sensing.
• Phase measurement errors, stemming from interferometer and laser instabilities, limit OTDR accuracy.
• Existing methods for phase unwrapping error reduction are often insufficient.

Purpose of the Study:

• To propose and experimentally validate a novel method for phase measurement error suppression in phase-sensitive OTDR.
• To enhance the accuracy and reliability of phase measurements in OTDR systems.
• To develop a method robust against common-mode noise and environmental fluctuations.

Main Methods:

• Implementation of a Mach-Zehnder interferometer utilizing 3x3 fiber couplers for enhanced stability.
• Utilization of all three photodetectors within the interferometer for comprehensive data acquisition.
• Development and application of a novel compensation scheme for accurate phase measurements.
• Experimental validation comparing measurements with and without the proposed compensation.

Main Results:

• The proposed method significantly suppresses phase measurement errors caused by interferometer and laser source instabilities.
• Employing three photodetectors improves phase unwrapping accuracy compared to using a single pair.
• The novel compensation scheme demonstrates a significant improvement in signal detection.
• The method enables tracking of slow temperature changes, a capability lacking in systems using simple low-pass filters.

Conclusions:

• The developed technique effectively compensates for common-mode noise, leading to superior phase measurement accuracy in phase-sensitive OTDR.
• The use of a 3x3 fiber coupler-based interferometer and a three-photodetector scheme offers a robust solution for OTDR error suppression.
• This advancement broadens the applicability of phase-sensitive OTDR, including its use for environmental monitoring like temperature tracking.