Extended Reference Interferometric Pattern for High Strain Optical Sensing
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Solution Overview
Problem
Optical strain sensing technologies face limitations in measuring high strains and maintaining signal quality for small strains, particularly due to physical deformation of the sensing waveguide, which can displace measurement segments and reduce correlation between reference and measurement patterns, especially when strains shift beyond the spectral range of measurement.
Innovation Solution
An interferometric measurement system records a reference interferometric pattern over an extended spectral range, allowing for registration with measurement patterns even if they are shifted beyond the measurement spectral range, using Optical Frequency Domain Reflectometry (OFDR) to determine strain by correlating spectral and temporal shifts, enabling continuous strain measurement along optical waveguides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cross-correlation approach is used to determine strain by comparing reference and measurement patterns, then strain measurement is achieved, but the measurement quality degrades when strain shifts the spectral pattern beyond the measurement range
Solution Approach 1:
The patent extends the reference measurement into a second spectral dimension beyond the normal measurement range. When strain shifts the measurement pattern outside the original spectral window, the extended reference provides overlapping spectral content in this extended dimension, maintaining correlation strength and measurement reliability for high strain conditions.
Solution Approach 2:
The extended reference pattern is recorded in advance during system calibration, capturing spectral content beyond the normal measurement range. This preliminary action ensures that when high strain occurs during operation, the shifted measurement pattern still finds matching spectral content in the pre-recorded extended reference, avoiding signal degradation.
2Ease of operation
If the spectral range of measurement is limited, then the measurement system operates within a defined range, but high strain measurements become impossible when the shifted pattern exceeds this range
Solution Approach 1:
By recording the reference pattern over an extended spectral range that exceeds the normal measurement range, the system creates a broader spectral dimension for comparison. This allows the measurement system to accommodate large strain-induced spectral shifts while maintaining the simplicity of operation within the normal measurement window.
Solution Approach 2:
The extended reference pattern serves multiple functions: it enables both low-strain measurements within the normal range and high-strain measurements when the pattern shifts beyond the normal range. This multi-functionality allows a single measurement system to handle the full spectrum of strain conditions without requiring separate measurement ranges.
3Measurement precision
If physical deformation of the waveguide is present before measurement, then the measurement segment may be displaced, but proper alignment requires knowledge of the strain state
Solution Approach 1:
The extended reference pattern creates a spectral fingerprint copy that accounts for physical displacement. By comparing the measurement pattern against this extended reference, the system can identify the correct segment alignment based on spectral matching alone, without requiring separate strain state monitoring or complex alignment procedures.
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 enhances the ability to measure high strains and maintain signal quality by decoupling the strain range from the measurement spectral range, allowing for robust strain sensing and extended measurement lengths, reducing signal degradation and enabling continuous strain profiling.
Implementation Method 1
Optical fiber strain sensing with fiber Bragg gratings uses a spectral shift induced by a strain on the fiber as a basic measurement technique. The shift in the Bragg spectrum is a result of the elongation or compression of the period of the periodic modulation of index that forms the Bragg grating. Strain is thus encoded onto wavelength and read out using a spectrometer.
Implementation Method 2
Interferometric detection circuitry detects and stores measurement interferometric pattern data associated with the segment of the optical waveguide
Data Source
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AI summary
An interferometric measurement system measures a parameter using at least one optical waveguide. A memory stores reference interferometric pattern data associated with a segment of the optical waveguide. Interferometric detection circuitry detects and stores measurement interferometric pattern data associated with the segment of the optical waveguide during a measurement operation. A spectral range of the reference interferometric pattern of the optical waveguide is greater than a spectral range of the measurement interferometric pattern of the optical waveguide. A processor shifts one or both of the measurement interferometric pattern data and the reference interferometric pattern data relative to the other to obtain a match and to use the match to measure the parameter. An example parameter is strain.