Double Bragg Grating Optical Fiber Sensor for Chiral Motion
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Solution Overview
Problem
Existing optical fiber Bragg grating sensors face challenges in accurately measuring complex and continuous body motions, particularly in chiral structures, due to limitations in detecting spatial motions and directional changes, which are essential for precise monitoring of dynamic and static equilibrium states.
Innovation Solution
A double Bragg grating structure with a helical core and a sub-grating configuration, where three or more basic Bragg gratings with long periods and a sub-grating with short periods are formed within the core, allowing for precise measurement of wavelength shifts and directional changes, enabling the detection of chiral motion and spatial body movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single Bragg grating is used in the optical fiber core, then the sensor structure is simple and easy to manufacture, but it cannot accurately measure complex spatial motions and directional changes in chiral structures
Solution Approach 1:
The optical fiber core is segmented into multiple distinct grating regions: a first Bragg grating with a first period, a second Bragg grating with a second period, and a third Bragg grating with a third period. Each grating segment responds to different aspects of the applied stimulus, enabling comprehensive measurement of complex spatial motions and directional changes through combined analysis of their respective wavelength shifts.
Solution Approach 2:
The patent introduces a longitudinal dimension to the grating structure by arranging multiple gratings with different periods along the length of the optical fiber core. This dimensional expansion allows the sensor to capture multi-axis motion information and chiral structure deformations that cannot be measured by a single grating, transforming the measurement capability from one-dimensional to multi-dimensional.
2Reliability
If the refractive index of the core is increased by adding specific material, then the light guiding performance is improved, but structural defects may be caused in the silica glass
Solution Approach 1:
Instead of changing the material composition of the core, the patent modifies the physical parameter of the grating period across different sections. The first, second, and third Bragg gratings have distinct periods that are optimized for their specific measurement functions. This parameter-based differentiation achieves enhanced light guiding performance and measurement capability without introducing material-related structural defects.
Solution Approach 2:
The patent replaces the material-based refractive index modification approach with a geometric-based grating period variation approach. Rather than adding specific materials to change the core's refractive index, the invention uses mechanically inscribed gratings with different periods to achieve the same functional outcome of enhancing light interaction and measurement precision without compromising structural integrity.
3Measurement precision
If a double Bragg grating structure with helical core is implemented, then the sensitivity and accuracy of motion measurement is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The manufacturing process is segmented into distinct inscription steps for each grating type. The first Bragg grating is inscribed with a first period, followed by inscription of the second grating with a second period, and finally the third grating with a third period. This segmented approach allows each grating to be optimized independently while maintaining overall manufacturing feasibility through systematic process organization.
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 sensitivity and accuracy of motion measurement, allowing for the precise tracking of dynamic and static body motions, including inflection points and direction changes, by modifying the refractive index and critical angle of light, thereby overcoming the limitations of traditional sensors in measuring complex body surfaces and spatial motions.
Implementation Method 1
The Bragg grating has a characteristic in that only a wavelength which satisfies the Bragg condition is reflected
Implementation Method 2
When a strong ultraviolet ray is irradiated onto the optical fiber core, a bonding structure of the material is modified to change the refractive index of the optical fiber
Implementation Method 3
The core with the helical structure moves a wavelength of the Bragg grating using an elastic wave in accordance with the helical structure
Data Source
AI summary
The exemplary embodiments provide an optical fiber sensor and a vector measuring device which measure a motion of a subject using a double Bragg grating formed in a core with a helical structure and measure a chiral motion inflection point vector.