FBG Opening Sensor with Tension Locking for Slow State Detection
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Solution Overview
Problem
Conventional optical fiber-based opening and closing detection sensors struggle to accurately detect slow changes in the state of manhole covers and similar objects due to temperature-induced deformations and refractive index variations, leading to decreased detection sensitivity and false temperature change detection.
Innovation Solution
The sensor employs a moving member with a locking part that applies or releases tension to a fiber Bragg grating (FBG) part, allowing for precise detection of state changes by shifting the Bragg wavelength, even at low frequency and slow change rates, using a configuration where the FBG part is linearly disposed and the moving member moves along the optical fiber axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the optical fiber is used to detect opened and closed states by monitoring reflection or scattering state changes, then the sensor can monitor multiple objects simultaneously without power feeding wiring, but the sensor output value changes due to temperature-induced deformation and refractive index variation, causing false detection or inability to detect slow state changes
Solution Approach 1:
The patent introduces a reference optical fiber as an intermediary element that is isolated from mechanical deformation but exposed to the same temperature environment. By comparing the output signal of the sensing optical fiber (which experiences both temperature and mechanical effects) with the reference optical fiber (which experiences only temperature effects), the system can subtract the temperature-induced signal component and isolate the mechanical deformation signal, thereby eliminating false detections caused by temperature variations
Solution Approach 2:
The patent implements a differential measurement system where the reference optical fiber provides a feedback signal representing the temperature environment. This feedback is subtracted from the sensing optical fiber output, creating a corrected signal that compensates for temperature effects in real-time, enabling accurate detection of slow state changes
2Stability of the object's composition
If the optical fiber is kept under deformation for a long period to maintain shape, then the fiber shape is stable, but when the object state changes slowly, the fiber cannot recover its original shape quickly, decreasing detection sensitivity
Solution Approach 1:
The patent segments the optical fiber system into two independent components: a sensing optical fiber that experiences mechanical deformation and a reference optical fiber that remains mechanically isolated. This segmentation allows the sensing fiber to maintain stable deformation for accurate shape detection while the reference fiber provides a stable baseline, enabling the system to detect both stable and transient state changes effectively
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 solution enables certain detection of slow and low-frequency changes in the opened and closed states, maintaining detection sensitivity and avoiding false temperature change detection, 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
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.