Optical Fiber Fiduciary Marks for Backscattering Localization
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Solution Overview
Problem
Existing optical fiber sensors using Rayleigh backscattering for distributed strain and temperature measurements face challenges in localization due to random spectral and spatial responses, requiring precise knowledge of group indices, especially in multicore fibers, and are prone to inaccuracies from waveguide property drifts and the need for continuous fiber gratings.
Innovation Solution
Incorporating fiduciary marks along the optical fiber that produce measurable changes in the backscattering pattern, allowing for accurate localization without continuous calibration or fiber gratings, by altering propagation properties during manufacturing, such as through actinic radiation exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Rayleigh back scattering is used for distributed sensing, then measurements can be performed at any part of the fiber array, but the spectral and spatial response is random and localization requires precise knowledge of group index
Solution Approach 1:
The patent introduces fiduciary marks as intermediary reference objects embedded in the optical fiber. These marks serve as mediators between the Rayleigh backscattering signal and the measurement system, providing known reference points that enable accurate localization without requiring precise knowledge of group index variations. The fiduciary marks create distinctive scattering patterns that can be identified and used to calibrate spatial measurements.
2Measurement precision
If fiber gratings are used to provide scattering, then localization accuracy is improved, but continuous fiber gratings require inscription along the entire length of the fiber adding cost and complexity
Solution Approach 1:
The patent segments the continuous fiber grating concept into discrete fiduciary marks distributed at specific locations along the optical fiber. Instead of inscribing gratings along the entire fiber length, only discrete reference points are marked. This segmentation maintains localization accuracy at reference points while dramatically reducing fabrication complexity and cost.
Solution Approach 2:
The patent applies partial action by implementing fiduciary marks only at specific critical locations along the fiber rather than continuous coverage. This partial marking provides sufficient reference points for accurate localization and measurement calibration without the excessive complexity of continuous grating inscription throughout the entire fiber length.
3Measurement precision
If accurate calibration of light propagation in each core is performed, then measurement accuracy is improved, but any drift in waveguide properties renders calibration inaccurate
Solution Approach 1:
The patent implements preliminary action by embedding fiduciary marks during fiber manufacturing that serve as permanent, stable reference points. These marks are established beforehand and remain invariant to waveguide property drifts. The fiduciary marks provide a stable reference framework that allows for recalibration or drift compensation without requiring absolute calibration stability of the waveguide properties.
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 reliable and accurate distance measurements along optical fibers with improved spatial resolution and reduced complexity, allowing for precise correlation of signals across multiple cores without requiring absolute calibration stability.
Implementation Method 1
One type of back scattering that has been proposed for use in fiber shape measurements is Rayleigh back scattering
Data Source
AI summary
An optical fiber having at least one fiduciary mark is provided. The at least one fiduciary mark is located at one or more axial positions along the optical fiber. The at least one fiduciary mark is configured to produce at least one change in a backscattering signal in the optical fiber. The at least one change in a backscattering signal may be an abrupt change in the backscattering signal. The abrupt change in the backscattering signal occurs over a length of the optical fiber that is of the order of or less than a spatial resolution of an interrogation system employed to detect the backscattering signal.