Optical Fiber Impact Detection via Wavelength Multiplexing
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Solution Overview
Problem
Conventional impact detection systems using optical fiber sensors struggle to accurately specify the existence, position, and magnitude of impacts on composite materials due to limitations in detecting changes in reflected light vibrations, especially when impacts occur at arbitrary positions and with varying magnitudes.
Innovation Solution
The system employs optical fiber sensors with grating portions that reflect specific wavelengths, distributed optical filters, and an arithmetic processing unit to analyze output values from multiple sensor sections, ensuring non-overlapping vibration bands and precise detection of impacts by separating changes in reflected light vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single optical fiber sensor with a grating portion is used to detect damage, then the structure strength is maintained, but the system cannot specify the existence, position, and magnitude of impacts at arbitrary positions
Solution Approach 1:
The optical fiber sensor is divided into multiple sensor sections along its length, with each section having a grating portion at a different position. This segmentation allows the system to detect impacts at multiple locations simultaneously, transforming a single-point detection system into a distributed detection system that can specify both the position and magnitude of impacts throughout the monitored structure.
2Strength
If the optical fiber diameter is thinned to 52 μm for easier embedding, then the structure strength is scarcely reduced, but the detection capability for arbitrary impacts is limited
Solution Approach 1:
The thinned optical fiber is segmented into multiple sensor sections, each capable of independent detection. This allows the system to maintain the structural advantages of thin fibers while achieving comprehensive impact detection capability through the distributed arrangement of multiple sensing points along the fiber length.
3Device complexity
If a piezo-element is fixed at a predetermined position to detect damage, then the detection system is simple, but it cannot detect impacts at arbitrary positions with high accuracy
Solution Approach 1:
The mechanical piezo-element detection system is replaced with an optical fiber-based detection system. Instead of using mechanical vibration elements fixed at predetermined positions, the invention uses optical fiber sections with grating portions that detect impacts through optical wavelength changes, providing both simplified integration and enhanced detection capability across multiple positions.
Solution Approach 2:
The single piezo-element is replaced by multiple optical sensor sections distributed along the fiber, enabling the system to detect impacts at various positions simultaneously while maintaining relatively simple system architecture through the use of a single optical fiber conduit.
4Adaptability or versatility
If the wavelength bands of sensor sections overlap, then the detection coverage is maximized, but the vibration bands cannot be distinguished, reducing detection accuracy
Solution Approach 1:
Each sensor section is assigned a specific, non-overlapping wavelength band, creating local differentiation in the optical domain. This allows the system to maintain comprehensive detection coverage across multiple sections while enabling clear distinction between vibrations from different locations through wavelength multiplexing, where each spatial location has a unique optical signature.
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
This configuration allows for high-accuracy detection of impacts by distinguishing between varying vibration bands and accurately determining the existence, position, and magnitude of impacts on composite materials.
Implementation Method 1
the grating portion is provided with a plurality of gratings each reflecting light, wavelength band of reflected light changes when a distance between the adjacent gratings changes
Implementation Method 2
the optical fiber vibrates the wavelength band depending on an elastic wave propagating through a subject to be inspected
Data Source
AI summary
Disclosed is an impact detection system including: an optical fiber including a plurality of sensor sections to reflect light, a wavelength band of the reflected light vibrates depending on an elastic wave propagating through a subject to be inspected; a light source to input light into the optical fiber; optical filters each connected to an output terminal of the optical fiber; and an arithmetic processing unit to detect the impact from output values of sensor sections, wherein the wavelength bands of the sensor sections in the optical fiber are distributed such that the vibration bands caused by the impact to be detected do not overlap with each other, and a pass band of the optical filter corresponding to one of the sensor sections is distributed in the vibration band caused by the detection object, and is distributed in both sides of a center of the wavelength band of the one sensor section.