Fiber Optic Strain Locking via Granule Interference Fit
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Solution Overview
Problem
Existing methods for attaching optical fibers to tools for strain measurement are hindered by the fragility of the fibers, which requires protective sheaths, and there is a need for reliable transmission of strain between these sheaths.
Innovation Solution
A fiber optic strain locking arrangement that uses a cable assembly with an optical fiber strain transmissively coupled to its outer radial surface, surrounded by tubing that is strain locked through an interference fit and/or adhesion, utilizing granules that can be embedded for enhanced strain transmission, including transient and thermal strains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical fibers are housed within protective sheaths, then the reliability of the optical fiber is improved, but the strain transmission between sheaths deteriorates
Solution Approach 1:
The protective structure is divided into multiple sheath segments (inner sheath and outer sheath) that can be separately optimized. The inner sheath provides direct protection to the optical fiber, while the outer sheath provides additional protection and strain transmission interface, allowing each segment to fulfill its specific function without compromising the other
Solution Approach 2:
The inner sheath is nested within the outer sheath, creating a layered protective structure. This nesting allows the optical fiber to be protected by the inner sheath while the outer sheath provides additional protection and serves as the interface for strain transmission through the locking mechanism
Solution Approach 3:
A locking mechanism acts as an intermediary between the inner and outer sheaths, providing a reliable connection that ensures strain transmission. The locking mechanism includes features such as ribs, grooves, or adhesive bonds that mechanically couple the sheaths together while allowing for controlled strain transfer
2Measurement precision
If the optical fiber is directly attached to the tool, then the strain measurement accuracy is improved, but the optical fiber fragility causes reliability deterioration
Solution Approach 1:
The sheath structure serves as an intermediary between the optical fiber and the external environment. It provides mechanical protection to the fragile optical fiber while maintaining strain transmission capability through the locking mechanism, allowing the fiber to be protected yet still accurately measure strain
Solution Approach 2:
The sheath is designed as a thin-walled structure that provides protection while remaining flexible enough to transmit strain. The thin wall allows strain to be transmitted through the sheath to the locking mechanism and ultimately to the optical fiber, while still providing necessary mechanical protection
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
Ensures reliable and accurate transmission of strain measurements, providing structural support to the optical fiber and maintaining strain transmissivity even with varying strains over time, such as those encountered in acoustics and vibrations.
Implementation Method 1
The strain locking being accomplished through either interference fit individually or a combination of interference fit and adhesion (via an adhesive 30), between the cable assembly 14 and the tubing 22. The interference fit including granules 26 that are at least partially embedded into at least one of the cable assembly 14 and the tubing 22.
Implementation Method 2
The strain locking being accomplished through either interference fit individually or a combination of interference fit and adhesion (via an adhesive 30), between the cable assembly 14 and the tubing 22.
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A fiber optic strain locking arrangement includes a cable assembly having an outer radial surface, an optical fiber strain transmissively coupled to the outer radial surface, and tubing disposed at the outer radial surface. The tubing is strain locked to the outer radial surface through at least one of interference fit with granules at least partially embedded into at least one of the tubing and the outer radial surface and adhesive bonding to both the tubing and the outer radial surface.