Optical Fiber Interferometric Data Registration via Grating Reflection Filtering
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Solution Overview
Problem
Existing optical fiber strain sensing technologies face challenges in accurately registering measurement data from multi-core optical fibers with semi-continuous Bragg gratings due to strong correlation peaks at multiples of the grating width, making it difficult to match specific locations along the fiber to corresponding reference data.
Innovation Solution
A data processing system that filters out reflections due to the repeated pattern of optical gratings, correlates filtered measurement data with reference data to produce correlation values, and identifies the location corresponding to the greatest correlation value, using techniques such as zero padding and parabolic fitting to achieve finer resolution and accurate registration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If simple spatial cross correlation is performed between measurement data and reference data, then correlation calculation is simple and fast, but the correlation peaks occur at multiples of Bragg grating width making it difficult to identify specific locations
Solution Approach 1:
The patent extracts and removes the periodic grating reflection components from the measurement data before performing cross-correlation. By eliminating these repeating patterns that cause multiple correlation peaks, the method isolates the unique Rayleigh backscatter signature at each location, enabling accurate identification of specific fiber positions while maintaining computational efficiency
Solution Approach 2:
The patent introduces Rayleigh backscatter as an intermediary signal component to enable accurate location identification. This naturally occurring random scattering provides a unique fingerprint for each fiber location that, when separated from the periodic grating reflections through filtering, serves as a reliable mediator for precise spatial registration between measurement and reference data
2Measurement precision
If semi-continuous Bragg gratings are written along each core to enable strain sensing, then continuous strain measurement is achieved, but the repeated pattern creates strong correlation peaks at multiples of grating width
Solution Approach 1:
The patent segments the optical signal into two distinct components: periodic grating reflections and random Rayleigh backscatter. By separating these segments through spectral filtering and processing, the method preserves the strain sensing capability provided by the continuous grating pattern while isolating the location-specific Rayleigh signature for accurate spatial identification
Solution Approach 2:
The patent converts the harmful effect of repeated grating patterns causing ambiguous correlation peaks into a beneficial separation process. By deliberately filtering out these repeating patterns, the method transforms the problem of signal repetition into an opportunity to isolate and enhance the unique Rayleigh backscatter signature, thereby improving location identification 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
This approach enables accurate identification of specific locations along the optical fiber, improving the registration of measurement data with reference data and enhancing the precision of strain profile measurements, even in the presence of fiber bending and helixed cores.
Implementation Method 1
measured from interferometric patterns corresponding to scatter reflections received from the core
Implementation Method 2
interferometric patterns corresponding to scatter reflections received from the core
Implementation Method 3
optical fiber having a core including multiple, closely-spaced optical gratings written along the core
Data Source
AI summary
A system and method are used for an optical fiber having a core multiple, closely-spaced optical gratings written along the core that create a repeated pattern in the core. A memory stores predetermined reference reflection data and measurement reflection data determined for a length of the core detected from interferometric patterns corresponding to scatter reflections received from the core. Data processing circuitry reduces or removes from the measurement reflection data information that corresponds to reflections due to the repeated pattern in the core to produce filtered measurement data. One or more portions of the filtered measurement data is/are correlated with one or more portions of the reference reflection data to produce multiple correlation values. The greatest of the multiple correlation values is determined, and a location along the fiber corresponding to the greatest correlation value is identified.