Miniature Fabry-Perot Optical Sensor with Integrated Silicon Diaphragm
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Solution Overview
Problem
Existing miniature fiber optic pressure sensors are either too large or fragile, making them unsuitable for applications requiring compactness and robustness, especially in harsh environments.
Innovation Solution
A miniature optical sensor design featuring a lead optical fiber with a spacer having an inwardly curved end surface and a flexible diaphragm that forms a Fabry-Perot cavity, allowing for a diameter as small as the lead fiber and enhanced robustness through thicker spacer walls and improved manufacturing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional housing design with silicon diaphragm and lead fiber is used, then the sensor can be made compact and immune to electromagnetic interference, but the sensor diameter becomes larger than the lead optic fiber diameter
Solution Approach 1:
The patent merges the housing and diaphragm into a single integrated silicon structure, eliminating the need for separate components. This integration allows the sensor to maintain electromagnetic interference immunity while reducing the overall sensor diameter to match the lead optic fiber diameter, resolving the contradiction between reliability and compactness.
Solution Approach 2:
The sensor structure is nested within the lead optic fiber, with the Fabry-Perot cavity and diaphragm arranged concentrically around the fiber. This nesting approach enables the sensor to be as small as the fiber itself while maintaining all necessary functional components for EMI immunity and pressure sensing.
2Volume of moving object
If ultra-miniature pressure sensors with polymer diaphragm are used, then the sensor size can be made close to the optical fiber diameter, but the sensor becomes fragile during manufacturing and use
Solution Approach 1:
The patent changes the material parameter from polymer to silicon, which has superior mechanical strength and rigidity. This material substitution maintains the ultra-miniature size while dramatically improving mechanical robustness, eliminating the fragility issue during manufacturing and use.
Solution Approach 2:
The sensor utilizes silicon as a composite structure integrating the housing, diaphragm, and spacer functions into a single monolithic piece. This composite approach eliminates weak interfaces between separate polymer components, resulting in a fragile-free miniature sensor that maintains both small size and high reliability.
3Volume of moving object
If photolithographic patterning techniques are used to manufacture miniature sensors, then the sensor can be made small at the tip of the lead optical fiber, but the manufacturing procedure becomes complicated requiring special tools and materials
Solution Approach 1:
The silicon structure serves multiple functions simultaneously - it forms the housing, the diaphragm, and the spacer for the Fabry-Perot cavity in a single self-contained component. This self-service design eliminates the need for complex photolithographic patterning and multiple assembly steps, simplifying manufacturing while maintaining ultra-miniature dimensions.
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 design achieves a compact, robust, and sensitive optical sensor that is insensitive to electromagnetic interference, with low drift and high thermal stability, suitable for various applications including medical and industrial uses.
Implementation Method 1
The flat cleaved lead fiber end and the diaphragm form two reflective surfaces that define a Fabry-Perot interferometer. The optical signal from the lead optical fiber is split into two paths which mutually interfere.
Implementation Method 2
The optical signal from the lead optical fiber is split into two paths which mutually interfere. The sum of their interference is function of the distance between the fiber end and the diaphragm position
Implementation Method 3
The diaphragm is flexible in response to the parameter, and defines a forward reflector of a sensing Fabry-Perot cavity within the optical sensor
Data Source
AI summary
A Fabry-Perot optical sensor for sensing a parameter such as pressure or the like is provided. The sensor includes a lead optical fiber from the end of which projects a spacer having an end surface curving inwardly. A diaphragm extends across the forward end of the spacer. The diaphragm is flexible in response to the parameter to be measured and defines a forward reflector of the Fabry-Perot cavity within the optical sensor. A method for manufacturing such a sensor is also provided.