Extended Reference Interferometric Pattern for High Strain Sensing
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Solution Overview
Problem
Optical strain sensing technologies face limitations in measuring high strains and maintaining signal-to-noise levels for small strains, especially when physical deformation of the sensing waveguide occurs, leading to misalignment of measurement segments and reduced correlation quality.
Innovation Solution
An interferometric measurement system records a reference interferometric pattern over an extended spectral and temporal range, allowing for registration with measurement patterns even when shifted beyond the measurement range, using Optical Frequency Domain Reflectometry (OFDR) to determine strain through spectral and temporal shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cross-correlation is used to determine strain shift, then strain measurement is achieved, but correlation quality degrades when strain shifts pattern points beyond spectral range
Solution Approach 1:
The patent extends the reference pattern into the temporal domain by applying inverse Fourier transform to frequency-shifted reference data. This creates a two-dimensional search space (frequency and time shifts) that allows the system to find matching points even when strain causes spectral shifts beyond the original measurement range, thereby maintaining correlation quality for high strain measurements
2Productivity
If measurement spectral range is reduced to increase scanning speed, then productivity improves, but measurement range becomes limited
Solution Approach 1:
The patent pre-calculates and stores an extended reference interferometric pattern covering a wider frequency range than the measurement scan. This preliminary action allows subsequent rapid measurements to reference against a comprehensive baseline, enabling fast scanning with limited spectral range while still achieving accurate strain measurement through the extended reference
Solution Approach 2:
By introducing temporal domain extension through Fourier transformation, the system compensates for the reduced spectral range. The extended reference pattern in both frequency and time domains provides additional matching points that maintain measurement capability even when the measurement scan covers a limited frequency range
3Reliability
If extended reference pattern is used to maintain correlation at high strain, then reliability improves, but device complexity increases
Solution Approach 1:
The patent replaces the need for physically extending the measurement spectral range with a computational approach. By using Fourier transforms to create temporal domain extensions of the reference pattern, the system achieves extended measurement capability through mathematical operations rather than hardware expansion, managing complexity through software-based signal processing
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 robust strain sensing across a wider range of strains, maintains signal quality, and allows for continuous measurement of strain along optical waveguides, overcoming limitations of existing technologies by decoupling measurement range from strain range and accommodating physical displacement.
Implementation Method 1
The Rayleigh scatter strain measurement technique is based on the fact that a given optical fiber possesses a random, broadband scattering profile that is both unique and repeatable. Analogous to a series of fiber Bragg gratings, when strained, this spectral fingerprint of the scatter shifts in wavelength.
Implementation Method 2
Optical strain sensing is a technology useful for measuring physical deformation of a waveguide caused by, for example, the change in tension, compression, or temperature of an optical fiber.
Implementation Method 3
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.
Data Source
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.