Transversal Load Insensitive Optical Waveguide Design
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Solution Overview
Problem
Optical fibers used for strain measurement are sensitive to transversal loads, which cause unwanted deformations and distortions in the fiber core, leading to inaccurate measurements due to changes in the reflection wavelength characteristics of the fiber Bragg grating.
Innovation Solution
A transversal load insensitive optical waveguide design featuring a primary section with a core and an outer cladding, where the mechanical connection between the exterior surface and the primary section surface deviates from being radial, deflecting radial loads and preventing direct deformation of the core, thereby maintaining the optical characteristics' integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical fiber with radial mechanical connection between cladding and core is used, then the fiber structure is simple and easy to manufacture, but the optical characteristics are sensitive to transversal loads causing measurement inaccuracies
Solution Approach 1:
The cladding structure is segmented into multiple discrete ribs rather than a continuous radial connection. These ribs are positioned at specific angular intervals around the core, creating a mechanically decoupled structure that allows transversal loads to be distributed and deflected away from the core while maintaining longitudinal strain transfer capability.
Solution Approach 2:
The mechanical connection between cladding and core is made asymmetric by positioning ribs at non-uniform angular intervals or with varying orientations. This asymmetric rib configuration creates directional stiffness that preferentially transfers longitudinal strain while deflecting transversal loads, breaking the radial symmetry that causes sensitivity to lateral pressure.
2Reliability
If the mechanical connection between outer cladding and primary section is radially directed, then the load transfer is direct and efficient, but radial loads cause deformation of the fiber core and distortion of reflection wavelength characteristics
Solution Approach 1:
The ribs serve as intermediary mechanical elements between the outer cladding and the core. Rather than providing direct radial support, the ribs act as force mediators that convert radial loads into axial forces through their inclined geometry, thereby protecting the core from direct radial compression while still enabling strain transfer for measurement.
Solution Approach 2:
The rib geometry parameters (angle, length, thickness) are optimized to change the force transmission characteristics. By adjusting the rib inclination angle and dimensions, the structure transforms radial load components into axial components, modifying the force transmission path to eliminate harmful radial stress on the core while maintaining reliable strain coupling.
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 design effectively reduces the impact of radial loads on the optical characteristics, allowing for accurate strain measurement by minimizing deformations and maintaining the fiber Bragg grating's periodicity, even under inhomogeneous load distributions, making it suitable for applications in optical sensors and structural health monitoring.
Implementation Method 1
said cladding structure is such that for at least part of a distance between any two radial corresponding points on said exterior surface and said primary section surface respectively, said mechanical connection deviates from being radial, for in use deflecting a radial directed load on an exterior surface of said outer cladding by means of said cladding structure
Implementation Method 2
strain on the fiber will change the periodicity of the fiber Bragg grating, providing a shift in the characteristic reflection wavelength of the grating
Data Source
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AI summary
Transversal load insensitive optical waveguide, and optical sensor comprising a wave guide. The present invention is directed to a transversal load insensitive optical waveguide, said waveguide (13) comprising a primary section (17) comprising a core (16), and said waveguide further comprising an outer cladding (18), wherein said primary section (17) comprises a primary section surface (22) and said outer cladding comprises an exterior surface (20) mechanically attached to said primary section surface by means of an interior cladding structure (26) forming a mechanical connection, and wherein said cladding structure is such that for at least part of a distance between each two radial corresponding points on said exterior surface and said primary section surface respectively, said mechanical connection deviates from being radial, for in use deflecting a radial directed load on an exterior surface of said outer cladding by means of said cladding structure.