Optical Fiber Clinometer with Pendulum and Fabry-Perot Cavity
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Solution Overview
Problem
Optical fiber clinometers have a weak impact-resisting capability and low sensitivity due to creepage at the bonding position of the fiber grating, affecting measurement precision in land deformation monitoring.
Innovation Solution
An optical fiber inclination measurement apparatus with a supporting mechanism, swinging mechanism, and measurement mechanism using a pendulum and cycloid, along with a differential structure involving two optical fibers and reflective films to form Fabry-Perot cavities, allowing for precise inclination measurement and improved impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fiber grating is directly bonded with sensitive structure, then the clinometer structure is simple, but the impact-resisting capability is weak and measurement precision deteriorates due to creepage
Solution Approach 1:
The patent introduces an optical fiber as an intermediary element between the sensitive structure and the measurement system. Instead of directly bonding fiber grating to the sensitive structure, the optical fiber transmits light signals that interact with the sensitive structure, eliminating direct mechanical bonding and preventing creepage while maintaining structural simplicity.
Solution Approach 2:
The patent replaces the mechanical bonding system with an optical measurement system. The fiber grating is substituted with an optical fiber-based Fabry-Perot cavity that uses optical interference principles instead of mechanical strain transfer, thereby eliminating the creepage issue associated with direct bonding while maintaining ease of manufacture.
2Ease of manufacture
If fiber grating is directly bonded with sensitive structure, then the clinometer structure is simple, but the impact-resisting capability is weak
Solution Approach 1:
The optical fiber serves as a mediator that decouples the sensitive structure from the measurement system. The optical fiber transmits measurement information without mechanical connection, providing isolation from impact forces while maintaining structural simplicity and improving impact-resisting capability.
Solution Approach 2:
The patent replaces the mechanical bonding system with an optical measurement system that uses light transmission instead of mechanical strain transfer. This substitution eliminates the weak link created by bonded connections, significantly improving impact-resisting capability while keeping the overall structure simple.
3Device complexity
If single optical fiber measurement is used, then the device complexity is low, but the measurement precision is affected by temperature variations
Solution Approach 1:
The patent divides the measurement system into two independent measurement channels using two optical fibers. Each fiber forms a separate Fabry-Perot cavity that measures inclination independently. This segmentation allows for differential measurement that cancels out temperature effects while maintaining relatively low device complexity.
Solution Approach 2:
The patent uses parameter changes by measuring the same physical quantity (inclination) through two different optical paths that are sensitive to different parameters. One measurement channel captures both inclination and temperature effects, while the other captures primarily temperature effects, allowing mathematical separation of the inclination component for improved temperature stability.
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 apparatus provides better impact-resisting capability and high sensitivity for land deformation monitoring, enabling accurate inclination measurement by converting pendulum displacement into cavity length variation, thus enhancing measurement precision and resilience.
Implementation Method 1
a pendulum and a cycloid, where two ends of the cycloid are connected to the base frame and the pendulum, respectively
Implementation Method 2
an end surface of the first optical fiber is disposed opposite to the first reflective film... receive the optical signal reflected by the first reflective film and the end surface of the first optical fiber to obtain a cavity length variation of a Fabry-Perot cavity
Implementation Method 3
receive the optical signal reflected by the first reflective film and the end surface of the first optical fiber
Data Source
AI summary
An optical fiber inclination measurement apparatus and a differential inclination measurement system are provided, which is related to the field of monitoring technology. The apparatus includes a supporting mechanism with a base and a base frame, a swinging mechanism with a pendulum, a cycloid, and a first reflective film is disposed on the pendulum. The measurement mechanism includes a first optical fiber, and an end surface of the first optical fiber is disposed opposite to the first reflective film. During an earthquake generating process, a landform changes and the pendulum swings, resulting in changes in displacement. The end surface of the first optical fiber together with the first reflective film form a Fabry-Perot cavity. The cavity length of the Fabry-Perot cavity changes before and after the landform deforms, and an angle of inclination is equal to a value obtained by dividing the cavity length variation of the Fabry-Perot cavity by the pendulum length.