Vibration Detection Using Vector Shape Tracking in Optical Fibers
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Solution Overview
Problem
Existing vibration detection methods using Distributed Acoustic Sensing (DAS) face challenges in accurately distinguishing between actual vibration-induced changes and noise-induced changes in scattered light intensity and phase, leading to potential overlooking of vibrations due to the complexity of determining reference values.
Innovation Solution
A vibration detection method that measures in-phase and quadrature components of scattered light, using reference and measurement vectors to determine vibration by tracking shape changes in triangular shapes formed by these vectors, allowing for a simpler and more accurate detection of physical vibrations in optical fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DAS-P (phase measurement method) is used to achieve quantitative vibration measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines DAS-I (intensity measurement) and DAS-P (phase measurement) into a unified vector-based detection system. By representing scattered light as complex vectors with both magnitude and phase information, the system integrates the simplicity of intensity measurement with the quantitative capability of phase measurement, resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent changes the measurement parameter from separate intensity or phase measurements to vector-based complex number representation. This parameter transformation allows the system to utilize both intensity and phase information simultaneously, achieving quantitative vibration measurement without requiring complex separate measurement systems
2Measurement precision
If DAS-P is used for quantitative vibration measurement, then measurement precision is improved, but signal processing complexity increases
Solution Approach 1:
The patent replaces complex signal processing operations with vector arithmetic operations. By representing scattered light as complex vectors, the system can use simple vector addition, subtraction, and rotation to process signals, avoiding the need for complex phase unwrapping and differential phase calculations required in traditional DAS-P
3Device complexity
If scattered light intensity is used for vibration detection, then device complexity is reduced, but measurement precision deteriorates due to inability to quantitatively calculate optical path length changes
Solution Approach 1:
The patent transforms the measurement parameter from simple intensity (magnitude only) to complex vector representation (magnitude and phase). This parameter change allows the system to extract quantitative optical path length information from the phase component of the vector, thereby improving measurement precision while maintaining the simplicity of intensity-based detection
4Measurement precision
If only phase change of scattered light is monitored, then measurement precision is improved, but reliability decreases when intensity change is large but phase change is small
Solution Approach 1:
The patent merges intensity and phase measurements into a unified vector-based detection system. By monitoring changes in the complex vector representation that incorporates both magnitude and phase information, the system ensures reliable vibration detection even when phase change is small but intensity change is significant, thereby improving detection reliability without sacrificing measurement precision
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 enables accurate detection of vibrations in optical fibers by using a simple determination reference, reducing the likelihood of overlooking vibrations, even when phase or intensity changes are small, and effectively combines the advantages of DAS-I and DAS-P.
Implementation Method 1
A method called DAS (Distributed Acoustic Sensing) in which a pulse test light enters a measurement target optical fiber and rearward scattered light obtained through Rayleigh scattering is detected
Data Source
AI summary
A vibration detection method is presented to accurately detect vibration physically applied to an optical fiber, using a simple determination reference. In a vibration detection method, scattered light of a given target segment of a measurement target fiber is indicated by vectors of an in-phase component and a quadrature component, and a triangular shape constituted by a near-end-side vector of the target segment and a far-end-side vector is used as a physical amount to be tracked. That is, it is determined whether or not there is vibration based on a change in shape of the triangular shape with respect to a reference state. This is a detection method in which DAS-I and DAS-P are combined, a simple determination reference such as shape change of a triangular shape is employed, and overlooking of vibration detection can be reduced.