Fiber Optic Strain Sensor with Reflective Surface
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Solution Overview
Problem
Current strain measurement technologies, such as resistance-type and semiconductor strain gages, face limitations in dynamic strain measurement due to electromagnetic interference, high cost, fragility, and complexity, while fiber optic Bragg grating sensors are expensive and have moderate strain detection limits, and interferometric sensors are complex and costly.
Innovation Solution
A fiber optic strain sensor using an optical fiber probe with a reflector body and a housing that modulates light reception based on strain-induced changes in the distance between the fiber end and the reflective surface, allowing for remote, sensitive, and multiplexed strain measurement without requiring interferometric techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistance-type strain gages are used, then cost is reduced and robustness is improved, but electromagnetic interference susceptibility increases and dynamic measurement capability deteriorates
Solution Approach 1:
The patent replaces electrical resistance measurement systems with an optical fiber-based measurement system. The optical fiber sensor uses light intensity modulation to measure strain, eliminating the electrical components that are susceptible to electromagnetic interference while maintaining robustness and dynamic measurement capability.
Solution Approach 2:
The patent introduces an optical fiber as an intermediary between the strain measurement point and the detection system. The optical fiber transmits light signals that are modulated by strain-induced changes in the reflector distance, providing immune transmission against electromagnetic interference while preserving signal integrity for dynamic measurements.
2Measurement precision
If semiconductor strain gages are used, then measurement sensitivity is improved, but cost increases, fragility increases, and electromagnetic interference susceptibility increases
Solution Approach 1:
The patent replaces fragile semiconductor strain gages with a robust optical fiber-based system. The optical fiber and reflector mechanism are mechanically robust while achieving high measurement sensitivity through light intensity modulation in response to strain-induced distance changes.
Solution Approach 2:
The patent uses an optical reflection principle where the reflector body creates a light intensity signal that copies the strain information. Instead of directly measuring electrical resistance changes in fragile semiconductor elements, the system captures strain information through optical reflection, achieving equivalent sensitivity with enhanced robustness.
3Length of moving object
If fiber optic Bragg grating sensors are used, then remote sensing capability is improved, but cost increases and strain detection limit deteriorates
Solution Approach 1:
The patent replaces Bragg grating wavelength modulation detection with a simpler light intensity modulation detection system. The optical fiber probe with reflector uses intensity-based measurement, which achieves comparable or better strain detection limits while reducing system cost and maintaining remote sensing capability through the inherent immunity of optical fibers to electromagnetic interference.
4Measurement precision
If interferometric fiber optic sensors are used, then measurement sensitivity is improved and electromagnetic interference immunity is improved, but device complexity increases and cost increases
Solution Approach 1:
The patent extracts the essential measurement function from complex interferometric systems by using a simplified light intensity modulation approach. Instead of using interferometric phase modulation, the system directly measures strain through changes in light intensity caused by reflector distance changes, achieving adequate sensitivity with dramatically reduced complexity.
Solution Approach 2:
The patent employs inexpensive optical components such as standard optical fibers, simple reflector bodies, and basic light sources/detectors rather than expensive interferometric instruments. This approach provides a cost-effective solution that achieves practical measurement sensitivity without the high cost and complexity of interferometric systems.
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 cost-effective, sensitive, and immune-to-electromagnetic-interference strain measurement system with a wide dynamic range, suitable for various applications, including remote sensing, by using a simple and robust design that maximizes light collection and minimizes complexity.
Implementation Method 1
The reflective surface is spaced apart at a distance d from the ends of the fibers and positioned to receive light from the end of the fiber and to reflect at least a portion of the light into the end of the fiber
Implementation Method 2
strain in the material causes a change in the distance d between the fiber end and the reflective surface, modulating the amount of light received in the receiving fiber
Data Source
AI summary
A strain sensor includes an optical fiber with at least one optical fiber, a reflector body with a reflective surface, a housing affixed to the optical fiber probe and to the reflector body. The reflective surface is spaced apart at a distance d from the ends of the probe's fibers and receives light from the end of the fiber and to reflect at least a portion of the light into the end of the fiber. The housing is attached to the fiber probe at a first end of the housing and attached to the reflector body at a second end of the housing. The housing is affixed to the material to be measured, and in the material causes a change in gap between the fiber end and the reflective surface, modulating the amount of light received in the receiving fiber, detectable by a photodetector connected to the receiving fiber.