OFDR Sensing System Dynamic Reference Spectrum Update
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Solution Overview
Problem
The existing optical frequency domain reflectometry (OFDR) sensing systems have limited sensing ranges for strain and temperature due to the frequency sweep width, as they cannot detect spectral shifts that occur outside the measurement band.
Innovation Solution
The system uses the spectrum from the immediately preceding measurement within the frequency sweep width as the reference spectrum, allowing for sequential updates and integration of spectral shifts to expand the sensing range without being limited by the frequency sweep width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed reference spectrum from initial measurement is used for cross-correlation, then the spectral shift detection is simple and fast, but the sensing range is limited by the frequency sweep width
Solution Approach 1:
The reference spectrum is dynamically updated from the immediately preceding measurement result instead of being fixed from initial measurement. This allows the reference spectrum to adapt to changing environmental conditions while maintaining the cross-correlation method's speed advantage. The dynamic update mechanism enables the system to track large spectral shifts that would otherwise fall outside the frequency sweep width.
Solution Approach 2:
The system continuously updates the reference spectrum using the result from the immediately preceding measurement, creating an unbroken chain of reference updates. This continuous adaptation ensures that the reference spectrum always reflects current conditions, allowing spectral shift detection to remain accurate even when total shifts exceed the original frequency sweep width.
2Adaptability or versatility
If the frequency sweep width is increased to expand sensing range, then the measurement band covers larger spectral shifts, but the measurement time increases
Solution Approach 1:
The total spectral shift measurement range is segmented into multiple smaller intervals, each handled by sequential measurements with fixed frequency sweep width. By updating the reference spectrum at each step and integrating the incremental shifts, the system achieves measurement of large total shifts without requiring a single wide frequency sweep, thus maintaining fast measurement speed while expanding sensing range.
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 the measurement of spectral shifts smaller than the frequency sweep width, effectively expanding the sensing range for strain and temperature detection while maintaining high-speed measurements.
Implementation Method 1
a spectrum S(ν) (FIG. 1(B)) can be analyzed by Fourier transforming a waveform r(τ) (FIG. 1(A)) of Rayleigh backscattered light with respect to the probe light of the optical fiber
Implementation Method 2
The spectrum S(ν) of the backscattered light fluctuates (spectral shift) with respect to a strain and a temperature of the optical fiber
Data Source
AI summary
An object of the present invention is to provide a sensing system, a sensing method, and an analyzing device using OFDR in which a sensing range of strain/temperature is less likely to be limited by a frequency sweep width.In the sensing method using OFDR, the sensing system according to the present invention employs sequential update, per measurement by one frequency sweep of the probe light, for setting the reference spectrum to the spectrum of an immediately preceding measurement, by which a spectral shift between an n-th measurement and an (n−1)th measurement is obtained, and the spectral shifts individually obtained between the measurements are integrated.