FBG Open-Close Sensor for Slow State Change Detection
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Solution Overview
Problem
Conventional optical fiber sensors struggle to accurately detect the opened and closed states of objects when changes occur slowly or at low frequencies due to temperature-induced deformation and refractive index variations, leading to decreased detection sensitivity.
Innovation Solution
An opening and closing detection sensor using an optical fiber with a fiber Bragg grating (FBG) is designed, featuring a moving member that changes position between open and closed states, applying or releasing tension to the FBG part, allowing for precise detection of slow state changes by shifting the Bragg wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical fiber sensor is used to detect opened and closed states, then the sensor can monitor multiple objects simultaneously without power feeding, but the detection sensitivity decreases when the opened and closed states change extremely slowly or at low frequencies due to temperature-induced deformation and refractive index variations
Solution Approach 1:
The optical fiber sensor is divided into multiple independent sensing units, each with its own FBG element. This segmentation allows each unit to independently detect state changes, improving the overall detection sensitivity and reliability for slow-changing states by distributing the detection function across multiple elements.
Solution Approach 2:
The invention uses Fiber Bragg Grating (FBG) technology which detects state changes through wavelength shifts rather than intensity changes. This parameter transformation from intensity-based detection to wavelength-based detection enables accurate measurement of slow state changes by measuring the Bragg wavelength shift caused by strain, which is not affected by temperature-induced intensity variations.
2Device complexity
If the optical fiber is deformed to detect opened and closed states by using reflection or scattering state changes, then the sensor structure is simple, but the response time is slow when temperature changes occur
Solution Approach 1:
The invention replaces the conventional mechanical deformation-based detection with an optical field-based FBG detection system. The FBG element detects strain through optical wavelength shifts, which occurs instantaneously without the thermal inertia affecting mechanical deformation. This substitution of detection mechanism eliminates the slow response caused by temperature-induced mechanical changes while maintaining structural simplicity.
3Stability of the object's composition
If the optical fiber is kept under external force for a long period of time in the closed state, then the fiber shape becomes fixed, but the fiber has difficulty recovering its original shape when the object opens, decreasing detection sensitivity
Solution Approach 1:
The FBG-based detection system dynamically responds to strain changes through optical wavelength shifts. When the object transitions from closed to open state, the FBG element experiences dynamic strain changes that are immediately captured as wavelength shifts. This dynamic optical response allows the system to detect state changes even when the fiber has been in a fixed shape for a long period, as the detection is based on the change in optical properties rather than mechanical recovery.
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 enables certain detection of slow and low-frequency changes in opened and closed states, improving sensitivity and accuracy by instantaneously applying or releasing tension to the FBG part when the moving member reaches a specific position.
Implementation Method 1
The optical fiber includes a fiber Bragg grating (FBG) part where a Bragg wavelength varies in response to an interval between the first base member and the second base member
Implementation Method 2
when an ambient temperature changes, the optical fiber is deformed by its expansion or contraction, and a refractive index of the optical fiber varies
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3(a)~3
AI summary
An opening and closing detection sensor of the present invention includes a fixed base, a moving base, an optical fiber, and a moving member. The moving base is disposed so as to be movable relative to the fixed base. The optical fiber includes an FBG part where a Bragg wavelength varies responding to an interval between the fixed base and the moving base. The moving member moves between a first position corresponding to either one of an opened state or a closed state of an object and a second position corresponding to the other state. The moving member includes a locking part. The locking part abuts on the moving base between a third position located between the first position and the second position, and the second position, thereby moving the moving base together with the moving member, and moving the moving base in a direction separated from the fixed base.