Full-scale OFDR-based distributed strain sensing with enhanced measurement accuracy.

Area of Science:

• Optical Engineering
• Metrology
• Fiber Optics Sensing

Background:

• Residual phase noise (RPN) significantly degrades strain sensing accuracy in optical frequency domain reflectometry (OFDR).
• Accurate strain measurement over long distances (100m level) is crucial for various structural health monitoring applications.

Purpose of the Study:

• To develop and validate a method for improving strain sensing accuracy in OFDR across full-scale distances.
• To minimize the impact of residual phase noise (RPN) on strain measurement precision.

Main Methods:

• Derivation of a quantitative relationship between RPN variance and interferometer delay.
• Design and implementation of a coded delay fiber module (OPEM) for dynamic optimal fiber length provision.
• Hardware-level suppression of RPN by analyzing noise and optimizing OPEM output configuration.

Main Results:

• Achieved strain sensing with a spatial resolution of 2mm.
• Demonstrated strain accuracy better than 1.5 με (2σ) across the full 100m scale.
• Approached the theoretical accuracy limit imposed by optical shot noise.

Conclusions:

• The proposed method effectively minimizes RPN, significantly enhancing strain sensing accuracy in OFDR systems.
• The OPEM module provides a hardware-level solution for RPN suppression, enabling high-precision long-distance strain measurements.
• This advancement pushes the boundaries of fiber optic sensing accuracy for demanding applications.