Twin-Core Fiber Grating Sensor for Decoupled Strain and Temperature Measurement
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Solution Overview
Problem
Existing fiber Bragg grating sensors face challenges in accurately isolating temperature and strain measurements due to interference from other factors such as hydrogen, deuterium, and acoustic waves, which cause changes in the grating wavelength, necessitating improved methods for decoupling these parameters.
Innovation Solution
A twin-core fiber configuration is employed, where both cores experience the same strain and temperature changes, allowing for the use of well-conditioned grating coefficients to decouple and measure strain and temperature independently, with each core having a different dopant regime to maintain distinct thermal and strain characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-core fiber Bragg grating sensor is used, then the device complexity is low, but the measurement precision deteriorates due to inability to isolate temperature and strain measurements
Solution Approach 1:
The single fiber is segmented into multiple independent cores, each containing a Bragg grating. This allows separate measurement channels within a single fiber structure, enabling temperature and strain decoupling while maintaining a compact form factor.
Solution Approach 2:
Multiple Bragg grating sensors are merged into a single multi-core fiber structure. This combines the functionality of multiple separate sensors into one integrated device, improving measurement precision while managing device complexity through unified structure.
2Measurement precision
If multiple Bragg gratings with different sensitivities are used to decouple temperature and strain, then the measurement precision improves, but the manufacturing precision requirements increase
Solution Approach 1:
Different dopant regimes are applied to different cores during manufacturing, creating inherent local differences in thermal and strain sensitivities. This eliminates the need for post-manufacturing sensitivity adjustment, reducing manufacturing precision requirements while maintaining measurement precision.
3Reliability
If conventional single-core fiber sensors are used, then the device complexity is low, but the reliability deteriorates due to interference from hydrogen, deuterium, and acoustic waves
Solution Approach 1:
The sensor system is segmented into multiple cores with different sensitivity characteristics. This segmentation allows differential measurement that cancels out common-mode interference from hydrogen, deuterium, and acoustic waves, improving reliability without complex isolation mechanisms.
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 approach enables precise measurement of temperature and strain by minimizing wavelength separation changes due to hydrogen or deuterium, and simplifies data analysis by using the difference in wavelength shifts between the cores to determine temperature changes.
Implementation Method 1
Each core has a reflective grating disposed therein such that the wavelength of light reflected by the gratings is in response to temperature and any strain applied to the sensor from a surrounding environment
Implementation Method 2
a single unitary ribbon-like structure can form the temperature sensor that has separate optical cores
Data Source
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AI summary
A twin core fiber for sensor applications is developed. It is particularly useful in de-coupling the strain and temperature and thus obtaining both measurement parameters at the same time and location. It is also particularly useful for measuring the temperature in a high humidity environment. The twin core fiber has two cores and each of the cores having a different dopant regime. Also, each of the cores includes a grating having substantially the same grating period.