Single-Grating Fiber Sensing for Temperature–Strain Separation
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Solution Overview
Problem
Existing methods for measuring temperature and deformation using fiber optic Bragg gratings require multiple fibers and gratings, leading to complexity and reduced precision when measurements are not made at the same location.
Innovation Solution
A method using a single optical fiber with a single Bragg grating, employing two sampling frequencies and blind source separation techniques, allows simultaneous measurement of temperature and deformation by converting data into the frequency domain for precise discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple fiber optic lines with Bragg gratings are used to measure temperature and strain, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent combines temperature and strain measurement capabilities into a single fiber optic line with a single Bragg grating. By using blind source separation techniques on signals acquired at different sampling frequencies, the system separates temperature and strain effects that both influence the Bragg wavelength, eliminating the need for multiple fibers and gratings while maintaining measurement capability
Solution Approach 2:
The invention changes the sampling frequency parameter to differentiate between temperature and strain measurements. By acquiring signals at both low sampling frequency (sensitive to temperature) and high sampling frequency (sensitive to strain), the system can separate the two measurement parameters through signal processing, reducing the physical number of sensors required
2Measurement precision
If Bragg gratings are placed close together to measure the same location, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple spatially close Bragg gratings into a single Bragg grating. By using blind source separation on frequency-domain signals, the system achieves the ability to measure both temperature and strain at the same location without requiring multiple gratings positioned in close proximity, thus simplifying the device while maintaining spatial measurement accuracy
3Device complexity
If a single fiber with two Bragg gratings is used, then device complexity is reduced, but measurement precision decreases because gratings are distant from each other
Solution Approach 1:
The invention changes from using spatial separation (multiple gratings at different positions) to frequency separation (single grating measured at different sampling frequencies) to differentiate between temperature and strain. This parameter change allows a single grating to provide both measurement functions with high spatial precision, eliminating the trade-off between device complexity and measurement accuracy
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
Enables precise, simultaneous measurement of temperature and deformation using a single fiber, reducing the number of fibers and gratings while maintaining measurement accuracy.
Implementation Method 1
temperature or strain measurements using fiber optic devices and Bragg gratings
Implementation Method 2
optical fiber line having a single Bragg grating
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for measuring temperature and deformation of a part or structure on the basis of a single line of optical fibre having a single Bragg grating that comprises the following steps: interrogating (50) the optical fibre based on two sampling frequencies; one being a low frequency (f sl ) and the other being a high frequency (f sh ), said low frequency f sl being suitable for sensing a slow rate of change corresponding to the temperature variation, and said high frequency f sh being suitable for sensing a fast rate of change corresponding to vibrations; - implementing an algorithmic block based on a blind-source-separation (BSS) technique, comprising a frequency analysis (200), a multivariate analysis (300) and higher-order statistics (400); - returning to the time domain via an inverse Fourier transform (600).