Helical Optical Fiber Deformation Measurement via Pulse Width Adjustment
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Solution Overview
Problem
Existing methods for measuring deformation in structures with helically wound optical sensing cables have poor spatial resolution, unable to accurately detect deformation at the pitch level of the helical wound optical fiber, which is crucial for monitoring fatigue in subsea structures like umbilicals and risers.
Innovation Solution
A method involving distributed measurements using a sensing optical fiber helically wound around a structure, adjusting pulse width to achieve a predefined spatial resolution within the range of the helical pitch ±50%, and analyzing the frequency gain spectrum to determine deformation by identifying peaks in the frequency curves, which correspond to strain and bending in the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If distributed measurement is performed using conventional methods, then deformation can be detected, but the spatial resolution is poor and unable to measure deformation at the pitch level of the helically wound optical fiber
Solution Approach 1:
The patent changes the parameter of pulse width in the optical measurement system to achieve the desired spatial resolution. By adjusting the pulse width parameter, the system can resolve deformation at the pitch level of the helically wound fiber without requiring complex hardware modifications
Solution Approach 2:
The patent employs dynamic curve fitting methods to extract deformation information from the frequency gain spectrum. The system dynamically adjusts measurement parameters and applies curve fitting algorithms to resolve the deformation at each pitch location along the fiber, enabling pitch-level spatial resolution through adaptive signal processing
2Reliability
If the spatial resolution is increased to measure deformation at pitch level, then accurate fatigue monitoring is achieved, but the measurement complexity and data processing requirements increase
Solution Approach 1:
The patent applies curve fitting to the frequency gain spectrum data before extracting deformation information. This preliminary processing step organizes the raw measurement data into a structured format, making subsequent deformation extraction more reliable and reducing the complexity of final analysis
Solution Approach 2:
The patent replaces complex mechanical measurement systems with optical-based distributed fiber sensing. By using optical frequency gain spectrum analysis and curve fitting, the system achieves high-resolution deformation measurement without the mechanical complexity of traditional strain gauges or displacement sensors
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides improved spatial resolution for deformation measurement, enabling accurate detection of strain and bending in subsea structures, thereby enhancing the monitoring of fatigue accumulation and structural integrity.
Implementation Method 1
providing the pulse pump signal with adjusted pulse width in the sensing optical fiber to generate scattering which is used to obtain said frequency gain spectrum
Data Source
AI summary
A method of determining deformation in a structure around which a sensing optical fiber is helically wound, includes performing a distributed measurement at a point along the fiber, to obtain a frequency gain spectrum at that point. Performing a distributed measurement includes, adjusting a pulse width of a pulse pump signal to achieve a predefined spatial resolution and providing the pulse pump signal with adjusted pulse width in the fiber to generate scattering, which is used to obtain the frequency gain spectrum. Identifying at least two curves which, when added together, best fit the frequency gain spectrum. Identifying the frequency at which peaks of the curves occur. Determining deformation in the structure by determining deformation in the fiber at the point using a frequency at which a peak of an identified curve occurs. The amount of deformation in the fiber corresponds to the amount of deformation in the structure.