Optical Fiber Shape Sensing With Asymmetric Cores for Small Bends
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Solution Overview
Problem
Existing optical fiber sensors face limitations in measuring small bend radii without reducing fiber core distance from the center axis and/or increasing the scan wavelength range, leading to reduced accuracy and sensitivity in shape sensing.
Innovation Solution
An optical fiber sensor design with a specific arrangement of fiber cores, including a first subset and a second subset arranged asymmetrically around the center axis, provides redundancy to measure smaller bend radii without altering the scan wavelength range or core distance, utilizing asymmetrical angular positions and potentially differing optical properties of the cores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the scan wavelength range is increased to measure smaller bend radii, then the measurement precision is improved, but the device complexity and signal quality deteriorate
Solution Approach 1:
The patent applies asymmetry by arranging fiber cores at non-uniform angular positions around the center axis. Specifically, the angular separation between adjacent fiber cores varies, with some separations being smaller and others larger. This asymmetric configuration allows the sensor to measure smaller bend radii without requiring an increased scan wavelength range, thereby resolving the contradiction between measurement precision and device complexity.
2Measurement precision
If the fiber core distance from the center axis is reduced to measure smaller bend radii, then the measurement precision is improved, but the sensitivity and signal quality worsen
Solution Approach 1:
The asymmetric angular positioning of fiber cores allows maintaining larger radial distances from the center axis while still achieving measurement of smaller bend radii. By strategically placing cores at varying angular positions, the system preserves sensitivity and signal quality without compromising the ability to measure small bend radii.
Solution Approach 2:
The patent transitions from a uniform radial arrangement to an asymmetric angular arrangement, effectively using the angular dimension more efficiently. This dimensional reconfiguration allows the system to achieve smaller minimum measurable bend radii while maintaining favorable signal-to-noise ratios by keeping fiber cores at optimal radial distances.
3Device complexity
If a standard symmetric arrangement of fiber cores is used, then the device complexity is reduced, but the ability to measure small bend radii is limited
Solution Approach 1:
The patent deliberately introduces asymmetry in the angular positions of fiber cores around the center axis. This asymmetric arrangement breaks the symmetry of conventional designs, enabling the measurement of smaller bend radii without significantly increasing device complexity. The non-uniform angular separations provide the necessary sensitivity variations to detect small bends while maintaining a relatively simple multi-core fiber structure.
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 allows for measuring smaller bend radii with improved accuracy and sensitivity by maintaining the scan wavelength range, enhancing the minimum measurable bend radius without compromising signal quality.
Implementation Method 1
an optical fiber sensor, also referred to as optical shape sensing fiber, is interrogated with light coupled into the fiber cores of the fiber, and distributed strain and temperature signals are obtained from back-scattered spectra obtained with an interrogator unit incorporating interferometers
Implementation Method 2
distributed strain and temperature signals are obtained from back-scattered spectra
Implementation Method 3
In case the fiber core is elongated (positively strained) relative to the reference measurement, the periodicity of the FBGs will increase, resulting in an increase in resonance wavelength
Implementation Method 4
the sensor will reflect the light of one particular wavelength, called the resonance wavelength
Data Source
AI summary
The present invention relates to an optical fiber sensor for shape sensing, comprising an optical fiber having embedded therein a number of at least four fiber cores (1 to 6) arranged at a distance from a longitudinal center axis (0) of the optical fiber, the number of fiber cores (1 to 6) including a first subset of at least two fiber cores (1, 3, 5) and a second subset of at least two fiber cores (2, 4, 6), the fiber cores (2, 4, 6) of the second subset being arranged to provide a redundancy in a shape sensing measurement of the fiber sensor (12′). The fiber cores (1, 3, 5) of the first subset are distributed in azimuthal direction around the center axis (0) with respect to one another, and each fiber core (2) of the second subset is arranged in non-equidistantly fashion in azimuthal direction around the center axis (0) with respect to two neighboring fiber cores (1, 3) of the first subset.