Monolithic Bragg Grating Sensor for Linear Force Measurement
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Solution Overview
Problem
Existing measuring devices with optical fiber Bragg gratings embedded in polymer substrates exhibit non-linear behavior due to mechanical property differences between the fiber and the substrate, making precise force determination challenging, especially when the force is applied off-center.
Innovation Solution
A measuring device with a substrate and optical waveguide made of the same material, where the waveguide and Bragg grating are monolithically integrated, ensuring identical mechanical properties and linear deformation response to applied forces, allowing for accurate force detection through spectroscopic analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical fiber Bragg grating is embedded in polymer layers to enable force measurement, then the measuring device can detect force through grating constant change, but the different mechanical properties between fiber and polymer cause non-linear behavior and reduce measurement precision
Solution Approach 1:
The patent merges the optical fiber Bragg grating and the substrate into a single monolithic structure made of the same material. This eliminates the interface between fiber and polymer layers, ensuring that both components experience identical deformation under applied force, thereby achieving linear behavior and improving measurement precision.
Solution Approach 2:
The patent applies homogeneity by using the same material for both the substrate and the optical waveguide containing the Bragg grating. This ensures uniform mechanical properties throughout the device, so that force application results in consistent deformation across all components, resolving the non-linearity issue caused by material heterogeneity.
2Ease of manufacture
If the optical fiber and polymer layers have different moduli of elasticity, then the device can be manufactured with simple embedding, but the compression experienced by polymer layers differs from that of the optical fiber, leading to non-linear grating constant change
Solution Approach 1:
The patent combines the optical fiber and substrate into a single monolithic component, eliminating the need for separate embedding processes. This unified structure ensures that the entire device responds uniformly to applied forces, achieving both ease of manufacture and high measurement precision simultaneously.
Solution Approach 2:
By using the same material for the substrate and optical waveguide, the patent creates a homogeneous structure with uniform mechanical properties. This eliminates the differential compression problem between dissimilar materials while maintaining manufacturing simplicity through single-material processing.
3Adaptability or versatility
If the force point of action is shifted within the surface of the measuring device, then the device can measure forces applied at different locations, but the force can no longer be reliably determined due to non-linear response
Solution Approach 1:
The monolithic structure with uniform material properties ensures that force application at any location on the substrate surface produces proportional and predictable deformation of the Bragg grating. This homogeneous response characteristic allows reliable force determination regardless of the exact point of application, enhancing both versatility and precision.
Data Source
AI summary
A measuring device is provided having at least one substrate, which contains or consists of a polymer or a glass, at least one optical waveguide being written in the substrate, in which at least one Bragg grating with a predeterminable grating constant is arranged, wherein the measuring device further includes an evaluation device, which is configured to determine a deformation of the substrate and/or a force acting on the substrate from a change in the grating constant and/or a change in the refractive index of the Bragg grating.