Optical Fiber Sensor With Gutter Cavity For Strain Measurement
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Solution Overview
Problem
Existing optical fiber strain sensors face challenges such as high temperature sensitivity, complex manufacturing processes, large size, and low sensitivity, which limit their practicality and cost-effectiveness for high-volume production and applications.
Innovation Solution
An optical fiber sensor design featuring a lead-in optical fiber coupled with a single-piece optical element having a reflective surface and a gutter, where the optical element's length is optimized to enhance strain sensitivity, allowing for simple signal interrogation and low temperature sensitivity, while maintaining a short optical cavity for high sensitivity and quality signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the cavity length is increased to enhance strain sensitivity, then measurement precision is improved, but optical losses increase and interference fringe visibility decreases
Solution Approach 1:
The patent changes the physical parameters of the optical element by creating a non-cylindrical shape with a gutter and retracted surface, allowing independent optimization of cavity length and outer dimension. This enables achieving L/Do ≥ 0.5 ratio that maximizes strain sensitivity while controlling optical losses through optimized light guidance in the gutter region.
Solution Approach 2:
The optical element features a retracted surface that is curved or non-planar, creating a specific light reflection pattern. This curvature design helps concentrate light within the gutter region, improving interference fringe visibility while maintaining long cavity length for enhanced strain sensitivity.
2Ease of manufacture
If a capillary structure is used to form the optical cavity, then manufacturing is simplified, but the sensor size increases and adhesion limitations arise
Solution Approach 1:
The optical element is segmented into functional regions: a gutter region for light guidance, a retracted surface for reflection, and a support base for mechanical stability. This segmentation allows the cavity to be formed within a compact footprint rather than requiring a large external capillary structure.
Solution Approach 2:
The optical cavity is nested within the optical element itself, with the gutter and retracted surface forming the cavity structure internally. This eliminates the need for an external capillary housing, reducing overall sensor size while maintaining the optical cavity functionality.
3Measurement precision
If fiber Bragg gratings are used for strain sensing, then measurement precision is improved, but temperature sensitivity increases and device complexity rises
Solution Approach 1:
The patent replaces the Bragg grating optical modulation mechanism with a mechanical Fabry-Perot interferometer system. The strain is measured through physical cavity length changes detected by interference patterns, simplifying the optical interaction mechanism and reducing temperature sensitivity compared to Bragg grating wavelength shifts.
4Measurement precision
If a single-piece optical element with long active length is used, then strain sensitivity is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The optical element exhibits local quality variations with different regions serving specific functions: the gutter region has specific depth and width for light guidance, the retracted surface has precise curvature for reflection, and the support base provides mechanical stability. These localized functional zones allow optimized manufacturing for each region rather than requiring uniform high precision throughout the entire element.
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 solution provides a robust, compact, and cost-effective optical fiber sensor with high strain sensitivity and low temperature sensitivity, suitable for high-volume production, and capable of measuring strain and pressure with improved accuracy and ease of signal processing.
Implementation Method 1
a pedestal with a reflective surface projecting rearwards
Implementation Method 2
the retracted surface and a second surface define an optical cavity
Data Source
Figure 1A~2
Figure 3~5
Figure 6~7
AI summary
Optical fiber sensors adapted to measure strain or pressure are disclosed. The optical fiber sensor has a lead-in optical fiber having an end surface at a forward end, and a first optical element having a body with an outer dimension, Do, a front end surface coupled to the lead-in optical fiber, a pedestal including a retracted surface that is spaced from the front end surface, the retracted surface at least partially defining an optical cavity, a gutter surrounding the pedestal, the gutter having a gutter depth defining an active region of length, L, the first optical element further exhibiting L/Do ≥ 0.5. Also provided are systems including the optical fiber sensor, and methods for manufacturing and using the optical fiber sensor. Numerous other aspects are provided.