Fiber Optic Cable Guides for Directional Acoustic Sensing
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Solution Overview
Problem
Existing distributed optical fiber sensing systems struggle to provide directional and location-specific information about acoustic vibrations along a fiber optic cable, especially when the cable is aligned differently from the direction of acoustic propagation, leading to difficulties in detecting and characterizing acoustic excitations effectively.
Innovation Solution
The system employs cable guides that support a fiber optic cable with nonparallel diffraction gratings aligned along different sensing axes, integrated with a tube to convey hydrocarbons, enabling detection of acoustic excitations from various directions using a distributed acoustic sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-direction fiber optic cable is used for distributed acoustic sensing, then the system structure is simple, but directional information and location-specific information about acoustic vibrations cannot be obtained
Solution Approach 1:
The patent transitions from single-direction sensing to multi-directional sensing by arranging diffraction gratings at different orientations (e.g., 0 degrees, 45 degrees, 90 degrees) around the cable. This dimensional expansion allows the system to detect acoustic vibrations from multiple directions simultaneously, providing directional information that was previously unavailable.
Solution Approach 2:
The sensing cable is divided into multiple sensing regions, each containing diffraction gratings with specific orientations. Each segment detects acoustic vibrations along its particular sensing axis, and the combined data from all segments provides comprehensive directional and location-specific information about acoustic sources.
2Measurement precision
If the fiber optic cable is aligned perpendicular to acoustic propagation direction, then the cable structure remains simple, but acoustic detection sensitivity decreases
Solution Approach 1:
By incorporating diffraction gratings at multiple orientations around the cable, the system becomes adaptable to acoustic waves propagating in any direction. The multi-axial grating arrangement ensures that at least some gratings will be optimally aligned with incoming acoustic waves regardless of their propagation direction, maintaining high detection sensitivity.
Solution Approach 2:
The cable with multi-oriented diffraction gratings serves multiple sensing functions simultaneously, detecting acoustic vibrations along multiple axes. This universal sensing capability allows the same cable structure to effectively detect acoustic waves regardless of their propagation direction, enhancing both sensitivity and adaptability.
3Measurement precision
If multiple diffraction gratings with nonparallel sensing axes are used, then directional and location-specific acoustic information is obtained, but the cable guide structure becomes more complex
Solution Approach 1:
Multiple diffraction gratings with different orientations are integrated into a single cable guide structure. The cable guide combines these individually oriented gratings into one unified system, allowing simultaneous multi-directional sensing without requiring separate cable installations. This merging reduces overall system complexity while maintaining location-specific detection capability.
Solution Approach 2:
The cable guide structure incorporates spatial arrangement of diffraction gratings in three-dimensional space with nonparallel sensing axes. This spatial configuration enables the system to resolve acoustic source locations by analyzing signals from gratings oriented at different angles, providing location-specific information through geometric arrangement rather than additional structural complexity.
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 configuration enhances the detection of acoustic excitations in three-dimensional space, providing precise directional and location-specific information about acoustic vibrations, improving the sensitivity and resolution of acoustic sensing.
Implementation Method 1
a first diffraction grating aligned with a first sensing axis and a second diffraction grating aligned with a second sensing axis
Data Source
AI summary
Cable guides that support a fiber optic cable relative to a tube, hydrocarbon conveyance systems including the cable guides, and methods of acoustically probing an elongate region. The cable guides include a cable retention structure with a first retention region configured to align a first diffraction grating along a first sensing axis and a second retention region configured to align a second diffraction grating along a second sensing axis that is nonparallel to the first sensing axis. The tube defines a tubular conduit configured to convey a hydrocarbon. The hydrocarbon conveyance systems include a tube, a distributed acoustic sensor, and a cable guide. The methods include transmitting an initiated optical signal and receiving a reflected optical signal that includes reflected portions that are reflected by a first diffraction grating and a second diffraction grating. The methods further include analyzing the reflected optical signal to detect an applied mechanical strain.