Twisted Sinusoidal Fiber Optic Cable for Broadside Acoustic Sensing
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Solution Overview
Problem
Conventional fiber optic Distributed Acoustic Sensing (DAS) systems are primarily sensitive to axial strain and become less sensitive or fail to detect acoustic signals traveling normal to the fiber axis, known as broadside signals, which is a limitation in seismic and microseismic applications where sensitivity to radial strain is crucial.
Innovation Solution
A distributed fiber optic cable with a sinusoidal optical fiber configuration that twists along its length, creating a twisted sinusoid shape, allowing for enhanced sensitivity to broadside acoustic signals by dividing the fiber into multiple channels to measure and differentiate radial and axial strain components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional straight fiber optic cable is used for DAS, then the system is simple and easy to manufacture, but it becomes less sensitive or fails to detect acoustic signals traveling normal to the fiber axis (broadside signals)
Solution Approach 1:
The optical fiber is configured in a sinusoidal shape instead of a straight line, creating curved paths that are sensitive to radial strain. The sinusoidal configuration with specific amplitude and wavelength parameters transforms the fiber's geometric form to detect broadside acoustic signals that would otherwise be missed by a straight fiber.
Solution Approach 2:
The invention transitions from a one-dimensional straight fiber to a two-dimensional sinusoidal path by introducing amplitude and wavelength parameters. This dimensional change allows the fiber to sample strain in multiple directions (axial and radial), enabling detection of acoustic signals from different propagation angles.
2Measurement precision
If the fiber is configured with sinusoidal paths to detect radial strain, then sensitivity to broadside signals improves, but the device structure becomes more complex
Solution Approach 1:
The sinusoidal fiber configuration is defined by specific parameters (amplitude A and wavelength λ) that can be optimized for different measurement requirements. By adjusting these parameters, the system achieves enhanced radial strain sensitivity while controlling the complexity of the fiber configuration through mathematical characterization rather than arbitrary geometric complexity.
3Adaptability or versatility
If a twisted sinusoidal configuration is implemented to distinguish radial from axial strain, then three-component sensing capability is achieved, but manufacturing complexity increases
Solution Approach 1:
The twisted sinusoidal fiber configuration serves multiple functions simultaneously: it detects axial strain through the sinusoidal path, radial strain through the twist component, and determines propagation direction through the combined geometric response. This multi-functional design enables three-component sensing with a single fiber configuration rather than requiring multiple separate 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
The twisted sinusoidal fiber optic cable significantly improves the detection of broadside acoustic signals, enabling the determination of the direction and magnitude of seismic waves, including those traveling at angles, thereby enhancing the sensitivity and accuracy in seismic monitoring applications.
Implementation Method 1
Because the cables typically comprise optically conducting fiber containing a plurality of backscattering inhomogeneities along the length of the fiber, such systems allow the distributed measurement of optical path length changes along an optical fiber by measuring backscattered light from a laser pulse input into the fiber.
Implementation Method 2
such systems allow the distributed measurement of optical path length changes along an optical fiber by measuring backscattered light from a laser pulse input into the fiber
Implementation Method 3
the Appendix attached hereto provides further discussion of the mathematics of sinusoidal fibers
Data Source
AI summary
A distributed fiber optic cable including an elongate body and optical fibers longitudinally housed in the elongate body. The optical fibers lie in in sinusoidal paths along longitudinal surfaces of a prism. The distributed fiber optic cable can be used for sensing an acoustic wave by measuring backscattered light from a laser pulse input into the optical fibers in the fiber optic cable.