FBG Optical Fibre Strain Sensing with Redundant Dual Interrogation
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Solution Overview
Problem
Existing systems for determining strain changes in optical fibers, particularly in aircraft, are expensive and lack robustness, accuracy, and versatility.
Innovation Solution
A method and system utilizing a combination of wavelength division multiplexing and time division multiplexing to determine strain changes in optical fibers with Fiber Bragg Grating patterns, incorporating redundant detector arrangements for enhanced reliability and flexibility, and automated operation to minimize downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two detector arrangements are used in parallel for redundancy, then reliability is improved, but cost increases due to expensive optical fibre
Solution Approach 1:
The patent combines two detector arrangements into a single shared system where both detectors can interrogate the same optical fibre containing Fiber Bragg Gratings. This merging approach maintains redundancy for reliability while eliminating the need for duplicate optical fibres, thereby resolving the contradiction between reliability and cost.
Solution Approach 2:
The optical fibre is designed to serve multiple functions by being shared between two detector arrangements. The same fibre can be interrogated by either detector independently or simultaneously, making the fibre a universal resource that provides redundancy without requiring duplicate fibres, thus reducing cost while maintaining reliability.
2Measurement precision
If multiple Fibre Bragg Gratings are inscribed along the optical fibre, then measurement capability is improved, but difficulty of detecting and measuring increases due to wavelength overlap
Solution Approach 1:
Each Fibre Bragg Grating is assigned a unique wavelength range through local customization of the grating characteristics. This local quality differentiation ensures that each grating's reflected wavelength is distinct and identifiable, eliminating measurement ambiguity even when multiple gratings are present along the fibre.
Solution Approach 2:
The patent utilizes parameter changes in the Fiber Bragg Gratings, specifically varying the Bragg wavelength of each grating through different inscription parameters. This allows multiple gratings to operate at different wavelengths, enabling precise strain measurement at multiple locations without wavelength overlap confusion.
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
The system provides accurate, cost-effective, and automated strain change detection with reduced downtime, enabling flexible deployment and improved decision-making for maintenance based on strain change analysis.
Implementation Method 1
Each Fibre Bragg Grating is active in its particular wavelength range within the electromagnetic spectrum and reflects a certain narrow wavelength band, within the particular wavelength range, depending on parameters like temperature, pressure, strain and indices of refraction. The reflected narrow wavelength band has a peak at the Bragg wavelength. A strain change results in a shift of the peak wavelength.
Data Source
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AI summary
The invention relates to a method for determining strain changes of an optical fibre (250) having Fiber Bragg Grating (FBG) patterns provided in at least one portion (Portion 1) of said optical fibre (250), said optical fibre (250) being connected between a first detector arrangement (210) and a second detector arrangement (220), the method comprising the steps of: - emitting (s410) light into said optical fibre (250) in a first direction (D1) from said first detector arrangement (210), receiving reflections from said (FBG) patterns of such emitted light by said first detector arrangement (210), and processing said reflections for determining a current strain change related to said optical fibre (250); - on the basis of predetermined criteria, emitting (s440) light into said optical fibre (250) in an opposite, second, direction (D2) from said second detector arrangement (220), receiving reflections from said (FBG) patterns of such emitted light by said second detector arrangement (220), and processing said reflections for determining a current strain change related to said optical fibre (250). The invention relates also to a computer program product comprising program code (P) for a computer (233; 243; 253; 500) for implementing a method according to the invention. The invention relates also to a system (289) for determining strain changes of an optical fibre (250). The invention also relates to a platform (100) being equipped with the system (289).