Optical Fiber Sensor Refractive Index Adjustment
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Solution Overview
Problem
In multi-core optical fiber sensors, the spirally wound outer peripheral cores create an optical path length difference with the central core, leading to positional accuracy issues and measurement inaccuracies, especially as the sensor length increases.
Innovation Solution
The effective refractive indices of the central and outer peripheral cores are adjusted to match their optical path lengths, with the outer peripheral core having a lower refractive index, and the molar concentration of dopants is optimized to minimize the optical path length difference, allowing for high measurement accuracy over extended lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the outer peripheral core is spirally wound around the central core to enable multi-core fiber configuration, then the sensor can measure distribution of physical quantities in the longitudinal direction, but an optical path length difference occurs between the central core and outer peripheral core leading to positional deviation and reduced measurement accuracy
Solution Approach 1:
The patent changes the refractive index parameter of the outer peripheral core by adjusting dopant concentration or composition, specifically setting it to be lower than that of the central core. This parameter modification compensates for the optical path length difference caused by the spiral winding, thereby reducing positional deviation and improving measurement accuracy while maintaining the multi-core configuration
2Length of moving object
If the sensor length is increased to extend measurement range, then the coverage area increases, but the optical path length difference between cores is accumulated and increased, making it difficult to secure measurement accuracy
Solution Approach 1:
By modifying the refractive index parameter of the outer peripheral core through dopant adjustment, the patent creates a compensatory effect that reduces optical path length differences. This allows the sensor to maintain high measurement accuracy even when the length is increased to extend the measurement coverage area
3Shape
If the distance between cores and number of spirals are increased to optimize sensor structure, then the structural performance improves, but the optical path length difference increases leading to reduced measurement accuracy
Solution Approach 1:
The patent introduces a new parameter control mechanism by adjusting the refractive index of the outer peripheral core. This allows the optical fiber structure to be optimized for structural performance while the refractive index difference compensates for the resulting optical path length differences, maintaining positional accuracy
Data Source
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AI summary
An optical fiber sensor includes a central core that is formed at a center of an optical fiber; and at least one outer peripheral core that is formed so as to spirally surround the central core, and the ratio between the effective refractive index of the central core and the effective refractive index of the outer peripheral core is set such that the optical path length difference between the central core and the outer peripheral core is smaller than the optical path length difference in a case where the effective refractive indices of the central core and the outer peripheral core are the same.